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diff --git a/doc/user-guide/user-guide.info b/doc/user-guide/user-guide.info new file mode 100644 index 000000000..078d62ade --- /dev/null +++ b/doc/user-guide/user-guide.info @@ -0,0 +1,2698 @@ +This is ../../../doc/user-guide/user-guide.info, produced by makeinfo +version 4.9 from ../../../doc/user-guide/user-guide.texi. + +START-INFO-DIR-ENTRY +* GlusterFS: (user-guide). GlusterFS distributed filesystem user guide +END-INFO-DIR-ENTRY + + This is the user manual for GlusterFS 2.0. + + Copyright (C) 2008,2007 <Z> Research, Inc. Permission is granted to +copy, distribute and/or modify this document under the terms of the GNU +Free Documentation License, Version 1.2 or any later version published +by the Free Software Foundation; with no Invariant Sections, no +Front-Cover Texts, and no Back-Cover Texts. A copy of the license is +included in the chapter entitled "GNU Free Documentation License". + + +File: user-guide.info, Node: Top, Next: Acknowledgements, Up: (dir) + +GlusterFS 2.0 User Guide +************************ + +This is the user manual for GlusterFS 2.0. + + Copyright (C) 2008,2007 <Z> Research, Inc. Permission is granted to +copy, distribute and/or modify this document under the terms of the GNU +Free Documentation License, Version 1.2 or any later version published +by the Free Software Foundation; with no Invariant Sections, no +Front-Cover Texts, and no Back-Cover Texts. A copy of the license is +included in the chapter entitled "GNU Free Documentation License". + +* Menu: + +* Acknowledgements:: +* Introduction:: +* Installation and Invocation:: +* Concepts:: +* Translators:: +* Usage Scenarios:: +* Troubleshooting:: +* GNU Free Documentation Licence:: +* Index:: + + --- The Detailed Node Listing --- + +Installation and Invocation + +* Pre requisites:: +* Getting GlusterFS:: +* Building:: +* Running GlusterFS:: +* A Tutorial Introduction:: + +Running GlusterFS + +* Server:: +* Client:: + +Concepts + +* Filesystems in Userspace:: +* Translator:: +* Volume specification file:: + +Translators + +* Storage Translators:: +* Client and Server Translators:: +* Clustering Translators:: +* Performance Translators:: +* Features Translators:: + +Storage Translators + +* POSIX:: + +Client and Server Translators + +* Transport modules:: +* Client protocol:: +* Server protocol:: + +Clustering Translators + +* Unify:: +* Replicate:: +* Stripe:: + +Performance Translators + +* Read Ahead:: +* Write Behind:: +* IO Threads:: +* IO Cache:: + +Features Translators + +* POSIX Locks:: +* Fixed ID:: + +Miscellaneous Translators + +* ROT-13:: +* Trace:: + + +File: user-guide.info, Node: Acknowledgements, Next: Introduction, Prev: Top, Up: Top + +Acknowledgements +**************** + +GlusterFS continues to be a wonderful and enriching experience for all +of us involved. + + GlusterFS development would not have been possible at this pace if +not for our enthusiastic users. People from around the world have +helped us with bug reports, performance numbers, and feature +suggestions. A huge thanks to them all. + + Matthew Paine - for RPMs & general enthu + + Leonardo Rodrigues de Mello - for DEBs + + Julian Perez & Adam D'Auria - for multi-server tutorial + + Paul England - for HA spec + + Brent Nelson - for many bug reports + + Jacques Mattheij - for Europe mirror. + + Patrick Negri - for TCP non-blocking connect. + http://gluster.org/core-team.php (<list-hacking@zresearch.com>) + <Z> Research + + +File: user-guide.info, Node: Introduction, Next: Installation and Invocation, Prev: Acknowledgements, Up: Top + +1 Introduction +************** + +GlusterFS is a distributed filesystem. It works at the file level, not +block level. + + A network filesystem is one which allows us to access remote files. A +distributed filesystem is one that stores data on multiple machines and +makes them all appear to be a part of the same filesystem. + + Need for distributed filesystems + + * Scalability: A distributed filesystem allows us to store more data + than what can be stored on a single machine. + + * Redundancy: We might want to replicate crucial data on to several + machines. + + * Uniform access: One can mount a remote volume (for example your + home directory) from any machine and access the same data. + +1.1 Contacting us +================= + +You can reach us through the mailing list *gluster-devel* +(<gluster-devel@nongnu.org>). + + You can also find many of the developers on IRC, on the `#gluster' +channel on Freenode (<irc.freenode.net>). + + The GlusterFS documentation wiki is also useful: +<http://gluster.org/docs/index.php/GlusterFS> + + For commercial support, you can contact <Z> Research at: + + 3194 Winding Vista Common + Fremont, CA 94539 + USA. + + Phone: +1 (510) 354 6801 + Toll free: +1 (888) 813 6309 + Fax: +1 (510) 372 0604 + + You can also email us at <support@zresearch.com>. + + +File: user-guide.info, Node: Installation and Invocation, Next: Concepts, Prev: Introduction, Up: Top + +2 Installation and Invocation +***************************** + +* Menu: + +* Pre requisites:: +* Getting GlusterFS:: +* Building:: +* Running GlusterFS:: +* A Tutorial Introduction:: + + +File: user-guide.info, Node: Pre requisites, Next: Getting GlusterFS, Up: Installation and Invocation + +2.1 Pre requisites +================== + +Before installing GlusterFS make sure you have the following components +installed. + +2.1.1 FUSE +---------- + +You'll need FUSE version 2.6.0 or higher to use GlusterFS. You can omit +installing FUSE if you want to build _only_ the server. Note that you +won't be able to mount a GlusterFS filesystem on a machine that does +not have FUSE installed. + + FUSE can be downloaded from: <http://fuse.sourceforge.net/> + + To get the best performance from GlusterFS, however, it is +recommended that you use our patched version of FUSE. See Patched FUSE +for details. + +2.1.2 Patched FUSE +------------------ + +The GlusterFS project maintains a patched version of FUSE meant to be +used with GlusterFS. The patches increase GlusterFS performance. It is +recommended that all users use the patched FUSE. + + The patched FUSE tarball can be downloaded from: + + <ftp://ftp.zresearch.com/pub/gluster/glusterfs/fuse/> + + The specific changes made to FUSE are: + + * The communication channel size between FUSE kernel module and + GlusterFS has been increased to 1MB, permitting large reads and + writes to be sent in bigger chunks. + + * The kernel's read-ahead boundry has been extended upto 1MB. + + * Block size returned in the `stat()'/`fstat()' calls tuned to 1MB, + to make cp and similar commands perform I/O using that block size. + + * `flock()' locking support has been added (although some rework in + GlusterFS is needed for perfect compliance). + +2.1.3 libibverbs (optional) +--------------------------- + +This is only needed if you want GlusterFS to use InfiniBand as the +interconnect mechanism between server and client. You can get it from: + + <http://www.openfabrics.org/downloads.htm>. + +2.1.4 Bison and Flex +-------------------- + +These should be already installed on most Linux systems. If not, use +your distribution's normal software installation procedures to install +them. Make sure you install the relevant developer packages also. + + +File: user-guide.info, Node: Getting GlusterFS, Next: Building, Prev: Pre requisites, Up: Installation and Invocation + +2.2 Getting GlusterFS +===================== + +There are many ways to get hold of GlusterFS. For a production +deployment, the recommended method is to download the latest release +tarball. Release tarballs are available at: +<http://gluster.org/download.php>. + + If you want the bleeding edge development source, you can get them +from the GNU Arch(1) repository. First you must install GNU Arch +itself. Then register the GlusterFS archive by doing: + + $ tla register-archive http://arch.sv.gnu.org/archives/gluster + + Now you can check out the source itself: + + $ tla get -A gluster@sv.gnu.org glusterfs--mainline--3.0 + + ---------- Footnotes ---------- + + (1) <http://www.gnu.org/software/gnu-arch/> + + +File: user-guide.info, Node: Building, Next: Running GlusterFS, Prev: Getting GlusterFS, Up: Installation and Invocation + +2.3 Building +============ + +You can skip this section if you're installing from RPMs or DEBs. + + GlusterFS uses the Autotools mechanism to build. As such, the +procedure is straight-forward. First, change into the GlusterFS source +directory. + + $ cd glusterfs-<version> + + If you checked out the source from the Arch repository, you'll need +to run `./autogen.sh' first. Note that you'll need to have Autoconf and +Automake installed for this. + + Run `configure'. + + $ ./configure + + The configure script accepts the following options: + +`--disable-ibverbs' + Disable the InfiniBand transport mechanism. + +`--disable-fuse-client' + Disable the FUSE client. + +`--disable-server' + Disable building of the GlusterFS server. + +`--disable-bdb' + Disable building of Berkeley DB based storage translator. + +`--disable-mod_glusterfs' + Disable building of Apache/lighttpd glusterfs plugins. + +`--disable-epoll' + Use poll instead of epoll. + +`--disable-libglusterfsclient' + Disable building of libglusterfsclient + + + Build and install GlusterFS. + + # make install + + The binaries (`glusterfsd' and `glusterfs') will be by default +installed in `/usr/local/sbin/'. Translator, scheduler, and transport +shared libraries will be installed in +`/usr/local/lib/glusterfs/<version>/'. Sample volume specification +files will be in `/usr/local/etc/glusterfs/'. This document itself can +be found in `/usr/local/share/doc/glusterfs/'. If you passed the +`--prefix' argument to the configure script, then replace `/usr/local' +in the preceding paths with the prefix. + + +File: user-guide.info, Node: Running GlusterFS, Next: A Tutorial Introduction, Prev: Building, Up: Installation and Invocation + +2.4 Running GlusterFS +===================== + +* Menu: + +* Server:: +* Client:: + + +File: user-guide.info, Node: Server, Next: Client, Up: Running GlusterFS + +2.4.1 Server +------------ + +The GlusterFS server is necessary to export storage volumes to remote +clients (See *Note Server protocol:: for more info). This section +documents the invocation of the GlusterFS server program and all the +command-line options accepted by it. + + Basic Options + +`-f, --volfile=<path>' + Use the volume file as the volume specification. + +`-s, --volfile-server=<hostname>' + Server to get volume file from. This option overrides -volfile + option. + +`-l, --log-file=<path>' + Specify the path for the log file. + +`-L, --log-level=<level>' + Set the log level for the server. Log level should be one of DEBUG, + WARNING, ERROR, CRITICAL, or NONE. + + Advanced Options + +`--debug' + Run in debug mode. This option sets -no-daemon, -log-level to + DEBUG and -log-file to console. + +`-N, --no-daemon' + Run glusterfsd as a foreground process. + +`-p, --pid-file=<path>' + Path for the PID file. + +`--volfile-id=<key>' + 'key' of the volfile to be fetched from server. + +`--volfile-server-port=<port-number>' + Listening port number of volfile server. + +`--volfile-server-transport=[socket|ib-verbs]' + Transport type to get volfile from server. [default: `socket'] + +`--xlator-options=<volume-name.option=value>' + Add/override a translator option for a volume with specified value. + + Miscellaneous Options + +`-?, --help' + Show this help text. + +`--usage' + Display a short usage message. + +`-V, --version' + Show version information. + + +File: user-guide.info, Node: Client, Prev: Server, Up: Running GlusterFS + +2.4.2 Client +------------ + +The GlusterFS client process is necessary to access remote storage +volumes and mount them locally using FUSE. This section documents the +invocation of the client process and all its command-line arguments. + + # glusterfs [options] <mountpoint> + + The `mountpoint' is the directory where you want the GlusterFS +filesystem to appear. Example: + + # glusterfs -f /usr/local/etc/glusterfs-client.vol /mnt + + The command-line options are detailed below. + + Basic Options + +`-f, --volfile=<path>' + Use the volume file as the volume specification. + +`-s, --volfile-server=<hostname>' + Server to get volume file from. This option overrides -volfile + option. + +`-l, --log-file=<path>' + Specify the path for the log file. + +`-L, --log-level=<level>' + Set the log level for the server. Log level should be one of DEBUG, + WARNING, ERROR, CRITICAL, or NONE. + + Advanced Options + +`--debug' + Run in debug mode. This option sets -no-daemon, -log-level to + DEBUG and -log-file to console. + +`-N, --no-daemon' + Run `glusterfs' as a foreground process. + +`-p, --pid-file=<path>' + Path for the PID file. + +`--volfile-id=<key>' + 'key' of the volfile to be fetched from server. + +`--volfile-server-port=<port-number>' + Listening port number of volfile server. + +`--volfile-server-transport=[socket|ib-verbs]' + Transport type to get volfile from server. [default: `socket'] + +`--xlator-options=<volume-name.option=value>' + Add/override a translator option for a volume with specified value. + +`--volume-name=<volume name>' + Volume name in client spec to use. Defaults to the root volume. + + FUSE Options + +`--attribute-timeout=<n>' + Attribute timeout for inodes in the kernel, in seconds. Defaults + to 1 second. + +`--disable-direct-io-mode' + Disable direct I/O mode in FUSE kernel module. + +`-e, --entry-timeout=<n>' + Entry timeout for directory entries in the kernel, in seconds. + Defaults to 1 second. + + Missellaneous Options + +`-?, --help' + Show this help information. + +`-V, --version' + Show version information. + + +File: user-guide.info, Node: A Tutorial Introduction, Prev: Running GlusterFS, Up: Installation and Invocation + +2.5 A Tutorial Introduction +=========================== + +This section will show you how to quickly get GlusterFS up and running. +We'll configure GlusterFS as a simple network filesystem, with one +server and one client. In this mode of usage, GlusterFS can serve as a +replacement for NFS. + + We'll make use of two machines; call them _server_ and _client_ (If +you don't want to setup two machines, just run everything that follows +on the same machine). In the examples that follow, the shell prompts +will use these names to clarify the machine on which the command is +being run. For example, a command that should be run on the server will +be shown with the prompt: + + [root@server]# + + Our goal is to make a directory on the _server_ (say, `/export') +accessible to the _client_. + + First of all, get GlusterFS installed on both the machines, as +described in the previous sections. Make sure you have the FUSE kernel +module loaded. You can ensure this by running: + + [root@server]# modprobe fuse + + Before we can run the GlusterFS client or server programs, we need +to write two files called _volume specifications_ (equivalently refered +to as _volfiles_). The volfile describes the _translator tree_ on a +node. The next chapter will explain the concepts of `translator' and +`volume specification' in detail. For now, just assume that the volfile +is like an NFS `/etc/export' file. + + On the server, create a text file somewhere (we'll assume the path +`/tmp/glusterfsd.vol') with the following contents. + + volume colon-o + type storage/posix + option directory /export + end-volume + + volume server + type protocol/server + subvolumes colon-o + option transport-type tcp + option auth.addr.colon-o.allow * + end-volume + + A brief explanation of the file's contents. The first section +defines a storage volume, named "colon-o" (the volume names are +arbitrary), which exports the `/export' directory. The second section +defines options for the translator which will make the storage volume +accessible remotely. It specifies `colon-o' as a subvolume. This +defines the _translator tree_, about which more will be said in the +next chapter. The two options specify that the TCP protocol is to be +used (as opposed to InfiniBand, for example), and that access to the +storage volume is to be provided to clients with any IP address at all. +If you wanted to restrict access to this server to only your subnet for +example, you'd specify something like `192.168.1.*' in the second +option line. + + On the client machine, create the following text file (again, we'll +assume the path to be `/tmp/glusterfs-client.vol'). Replace +_server-ip-address_ with the IP address of your server machine. If you +are doing all this on a single machine, use `127.0.0.1'. + + volume client + type protocol/client + option transport-type tcp + option remote-host _server-ip-address_ + option remote-subvolume colon-o + end-volume + + Now we need to start both the server and client programs. To start +the server: + + [root@server]# glusterfsd -f /tmp/glusterfs-server.vol + + To start the client: + + [root@client]# glusterfs -f /tmp/glusterfs-client.vol /mnt/glusterfs + + You should now be able to see the files under the server's `/export' +directory in the `/mnt/glusterfs' directory on the client. That's it; +GlusterFS is now working as a network file system. + + +File: user-guide.info, Node: Concepts, Next: Translators, Prev: Installation and Invocation, Up: Top + +3 Concepts +********** + +* Menu: + +* Filesystems in Userspace:: +* Translator:: +* Volume specification file:: + + +File: user-guide.info, Node: Filesystems in Userspace, Next: Translator, Up: Concepts + +3.1 Filesystems in Userspace +============================ + +A filesystem is usually implemented in kernel space. Kernel space +development is much harder than userspace development. FUSE is a kernel +module/library that allows us to write a filesystem completely in +userspace. + + FUSE consists of a kernel module which interacts with the userspace +implementation using a device file `/dev/fuse'. When a process makes a +syscall on a FUSE filesystem, VFS hands the request to the FUSE module, +which writes the request to `/dev/fuse'. The userspace implementation +polls `/dev/fuse', and when a request arrives, processes it and writes +the result back to `/dev/fuse'. The kernel then reads from the device +file and returns the result to the user process. + + In case of GlusterFS, the userspace program is the GlusterFS client. +The control flow is shown in the diagram below. The GlusterFS client +services the request by sending it to the server, which in turn hands +it to the local POSIX filesystem. + + + Fig 1. Control flow in GlusterFS + + +File: user-guide.info, Node: Translator, Next: Volume specification file, Prev: Filesystems in Userspace, Up: Concepts + +3.2 Translator +============== + +The _translator_ is the most important concept in GlusterFS. In fact, +GlusterFS is nothing but a collection of translators working together, +forming a translator _tree_. + + The idea of a translator is perhaps best understood using an +analogy. Consider the VFS in the Linux kernel. The VFS abstracts the +various filesystem implementations (such as EXT3, ReiserFS, XFS, etc.) +supported by the kernel. When an application calls the kernel to +perform an operation on a file, the kernel passes the request on to the +appropriate filesystem implementation. + + For example, let's say there are two partitions on a Linux machine: +`/', which is an EXT3 partition, and `/usr', which is a ReiserFS +partition. Now if an application wants to open a file called, say, +`/etc/fstab', then the kernel will internally pass the request to the +EXT3 implementation. If on the other hand, an application wants to +read a file called `/usr/src/linux/CREDITS', then the kernel will call +upon the ReiserFS implementation to do the job. + + The "filesystem implementation" objects are analogous to GlusterFS +translators. A GlusterFS translator implements all the filesystem +operations. Whereas in VFS there is a two-level tree (with the kernel +at the root and all the filesystem implementation as its children), in +GlusterFS there exists a more elaborate tree structure. + + We can now define translators more precisely. A GlusterFS translator +is a shared object (`.so') that implements every filesystem call. +GlusterFS translators can be arranged in an arbitrary tree structure +(subject to constraints imposed by the translators). When GlusterFS +receives a filesystem call, it passes it on to the translator at the +root of the translator tree. The root translator may in turn pass it on +to any or all of its children, and so on, until the leaf nodes are +reached. The result of a filesystem call is communicated in the reverse +fashion, from the leaf nodes up to the root node, and then on to the +application. + + So what might a translator tree look like? + + + Fig 2. A sample translator tree + + The diagram depicts three servers and one GlusterFS client. It is +important to note that conceptually, the translator tree spans machine +boundaries. Thus, the client machine in the diagram, `10.0.0.1', can +access the aggregated storage of the filesystems on the server machines +`10.0.0.2', `10.0.0.3', and `10.0.0.4'. The translator diagram will +make more sense once you've read the next chapter and understood the +functions of the various translators. + + +File: user-guide.info, Node: Volume specification file, Prev: Translator, Up: Concepts + +3.3 Volume specification file +============================= + +The volume specification file describes the translator tree for both the +server and client programs. + + A volume specification file is a sequence of volume definitions. +The syntax of a volume definition is explained below: + + *volume* _volume-name_ + *type* _translator-name_ + *option* _option-name_ _option-value_ + ... + *subvolumes* _subvolume1_ _subvolume2_ ... + *end-volume* + + ... + +_volume-name_ + An identifier for the volume. This is just a human-readable name, + and can contain any alphanumeric character. For instance, + "storage-1", "colon-o", or "forty-two". + +_translator-name_ + Name of one of the available translators. Example: + `protocol/client', `cluster/unify'. + +_option-name_ + Name of a valid option for the translator. + +_option-value_ + Value for the option. Everything following the "option" keyword to + the end of the line is considered the value; it is up to the + translator to parse it. + +_subvolume1_, _subvolume2_, ... + Volume names of sub-volumes. The sub-volumes must already have + been defined earlier in the file. + + There are a few rules you must follow when writing a volume +specification file: + + * Everything following a ``#'' is considered a comment and is + ignored. Blank lines are also ignored. + + * All names and keywords are case-sensitive. + + * The order of options inside a volume definition does not matter. + + * An option value may not span multiple lines. + + * If an option is not specified, it will assume its default value. + + * A sub-volume must have already been defined before it can be + referenced. This means you have to write the specification file + "bottom-up", starting from the leaf nodes of the translator tree + and moving up to the root. + + A simple example volume specification file is shown below: + + # This is a comment line + volume client + type protocol/client + option transport-type tcp + option remote-host localhost # Also a comment + option remote-subvolume brick + # The subvolumes line may be absent + end-volume + + volume iot + type performance/io-threads + option thread-count 4 + subvolumes client + end-volume + + volume wb + type performance/write-behind + subvolumes iot + end-volume + + +File: user-guide.info, Node: Translators, Next: Usage Scenarios, Prev: Concepts, Up: Top + +4 Translators +************* + +* Menu: + +* Storage Translators:: +* Client and Server Translators:: +* Clustering Translators:: +* Performance Translators:: +* Features Translators:: +* Miscellaneous Translators:: + + This chapter documents all the available GlusterFS translators in +detail. Each translator section will show its name (for example, +`cluster/unify'), briefly describe its purpose and workings, and list +every option accepted by that translator and their meaning. + + +File: user-guide.info, Node: Storage Translators, Next: Client and Server Translators, Up: Translators + +4.1 Storage Translators +======================= + +The storage translators form the "backend" for GlusterFS. Currently, +the only available storage translator is the POSIX translator, which +stores files on a normal POSIX filesystem. A pleasant consequence of +this is that your data will still be accessible if GlusterFS crashes or +cannot be started. + + Other storage backends are planned for the future. One of the +possibilities is an Amazon S3 translator. Amazon S3 is an unlimited +online storage service accessible through a web services API. The S3 +translator will allow you to access the storage as a normal POSIX +filesystem. (1) + +* Menu: + +* POSIX:: +* BDB:: + + ---------- Footnotes ---------- + + (1) Some more discussion about this can be found at: + +http://developer.amazonwebservices.com/connect/message.jspa?messageID=52873 + + +File: user-guide.info, Node: POSIX, Next: BDB, Up: Storage Translators + +4.1.1 POSIX +----------- + + type storage/posix + + The `posix' translator uses a normal POSIX filesystem as its +"backend" to actually store files and directories. This can be any +filesystem that supports extended attributes (EXT3, ReiserFS, XFS, +...). Extended attributes are used by some translators to store +metadata, for example, by the replicate and stripe translators. See +*Note Replicate:: and *Note Stripe::, respectively for details. + +`directory <path>' + The directory on the local filesystem which is to be used for + storage. + + +File: user-guide.info, Node: BDB, Prev: POSIX, Up: Storage Translators + +4.1.2 BDB +--------- + + type storage/bdb + + The `BDB' translator uses a Berkeley DB database as its "backend" to +actually store files as key-value pair in the database and directories +as regular POSIX directories. Note that BDB does not provide extended +attribute support for regular files. Do not use BDB as storage +translator while using any translator that demands extended attributes +on "backend". + +`directory <path>' + The directory on the local filesystem which is to be used for + storage. + +`mode [cache|persistent] (cache)' + When BDB is run in `cache' mode, recovery of back-end is not + completely guaranteed. `persistent' guarantees that BDB can + recover back-end from Berkeley DB even if GlusterFS crashes. + +`errfile <path>' + The path of the file to be used as `errfile' for Berkeley DB to + report detailed error messages, if any. Note that all the contents + of this file will be written by Berkeley DB, not GlusterFS. + +`logdir <path>' + + +File: user-guide.info, Node: Client and Server Translators, Next: Clustering Translators, Prev: Storage Translators, Up: Translators + +4.2 Client and Server Translators +================================= + +The client and server translator enable GlusterFS to export a +translator tree over the network or access a remote GlusterFS server. +These two translators implement GlusterFS's network protocol. + +* Menu: + +* Transport modules:: +* Client protocol:: +* Server protocol:: + + +File: user-guide.info, Node: Transport modules, Next: Client protocol, Up: Client and Server Translators + +4.2.1 Transport modules +----------------------- + +The client and server translators are capable of using any of the +pluggable transport modules. Currently available transport modules are +`tcp', which uses a TCP connection between client and server to +communicate; `ib-sdp', which uses a TCP connection over InfiniBand, and +`ibverbs', which uses high-speed InfiniBand connections. + + Each transport module comes in two different versions, one to be +used on the server side and the other on the client side. + +4.2.1.1 TCP +........... + +The TCP transport module uses a TCP/IP connection between the server +and the client. + + option transport-type tcp + + The TCP client module accepts the following options: + +`non-blocking-connect [no|off|on|yes] (on)' + Whether to make the connection attempt asynchronous. + +`remote-port <n> (6996)' + Server port to connect to. + +`remote-host <hostname> *' + Hostname or IP address of the server. If the host name resolves to + multiple IP addresses, all of them will be tried in a round-robin + fashion. This feature can be used to implement fail-over. + + The TCP server module accepts the following options: + +`bind-address <address> (0.0.0.0)' + The local interface on which the server should listen to requests. + Default is to listen on all interfaces. + +`listen-port <n> (6996)' + The local port to listen on. + +4.2.1.2 IB-SDP +.............. + + option transport-type ib-sdp + + kernel implements socket interface for ib hardware. SDP is over +ib-verbs. This module accepts the same options as `tcp' + +4.2.1.3 ibverbs +............... + + option transport-type tcp + + InfiniBand is a scalable switched fabric interconnect mechanism +primarily used in high-performance computing. InfiniBand can deliver +data throughput of the order of 10 Gbit/s, with latencies of 4-5 ms. + + The `ib-verbs' transport accesses the InfiniBand hardware through +the "verbs" API, which is the lowest level of software access possible +and which gives the highest performance. On InfiniBand hardware, it is +always best to use `ib-verbs'. Use `ib-sdp' only if you cannot get +`ib-verbs' working for some reason. + + The `ib-verbs' client module accepts the following options: + +`non-blocking-connect [no|off|on|yes] (on)' + Whether to make the connection attempt asynchronous. + +`remote-port <n> (6996)' + Server port to connect to. + +`remote-host <hostname> *' + Hostname or IP address of the server. If the host name resolves to + multiple IP addresses, all of them will be tried in a round-robin + fashion. This feature can be used to implement fail-over. + + The `ib-verbs' server module accepts the following options: + +`bind-address <address> (0.0.0.0)' + The local interface on which the server should listen to requests. + Default is to listen on all interfaces. + +`listen-port <n> (6996)' + The local port to listen on. + + The following options are common to both the client and server +modules: + + If you are familiar with InfiniBand jargon, the mode is used by +GlusterFS is "reliable connection-oriented channel transfer". + +`ib-verbs-work-request-send-count <n> (64)' + Length of the send queue in datagrams. [Reason to + increase/decrease?] + +`ib-verbs-work-request-recv-count <n> (64)' + Length of the receive queue in datagrams. [Reason to + increase/decrease?] + +`ib-verbs-work-request-send-size <size> (128KB)' + Size of each datagram that is sent. [Reason to increase/decrease?] + +`ib-verbs-work-request-recv-size <size> (128KB)' + Size of each datagram that is received. [Reason to + increase/decrease?] + +`ib-verbs-port <n> (1)' + Port number for ib-verbs. + +`ib-verbs-mtu [256|512|1024|2048|4096] (2048)' + The Maximum Transmission Unit [Reason to increase/decrease?] + +`ib-verbs-device-name <device-name> (first device in the list)' + InfiniBand device to be used. + + For maximum performance, you should ensure that the send/receive +counts on both the client and server are the same. + + ib-verbs is preferred over ib-sdp. + + +File: user-guide.info, Node: Client protocol, Next: Server protocol, Prev: Transport modules, Up: Client and Server Translators + +4.2.2 Client +------------ + + type procotol/client + + The client translator enables the GlusterFS client to access a +remote server's translator tree. + +`transport-type [tcp,ib-sdp,ib-verbs] (tcp)' + The transport type to use. You should use the client versions of + all the transport modules (`tcp', `ib-sdp', `ib-verbs'). + +`remote-subvolume <volume_name> *' + The name of the volume on the remote host to attach to. Note that + this is _not_ the name of the `protocol/server' volume on the + server. It should be any volume under the server. + +`transport-timeout <n> (120- seconds)' + Inactivity timeout. If a reply is expected and no activity takes + place on the connection within this time, the transport connection + will be broken, and a new connection will be attempted. + + +File: user-guide.info, Node: Server protocol, Prev: Client protocol, Up: Client and Server Translators + +4.2.3 Server +------------ + + type protocol/server + + The server translator exports a translator tree and makes it +accessible to remote GlusterFS clients. + +`client-volume-filename <path> (<CONFDIR>/glusterfs-client.vol)' + The volume specification file to use for the client. This is the + file the client will receive when it is invoked with the + `--server' option (*Note Client::). + +`transport-type [tcp,ib-verbs,ib-sdp] (tcp)' + The transport to use. You should use the server versions of all + the transport modules (`tcp', `ib-sdp', `ib-verbs'). + +`auth.addr.<volume name>.allow <IP address wildcard pattern>' + IP addresses of the clients that are allowed to attach to the + specified volume. This can be a wildcard. For example, a wildcard + of the form `192.168.*.*' allows any host in the `192.168.x.x' + subnet to connect to the server. + + + +File: user-guide.info, Node: Clustering Translators, Next: Performance Translators, Prev: Client and Server Translators, Up: Translators + +4.3 Clustering Translators +========================== + +The clustering translators are the most important GlusterFS +translators, since it is these that make GlusterFS a cluster +filesystem. These translators together enable GlusterFS to access an +arbitrarily large amount of storage, and provide RAID-like redundancy +and distribution over the entire cluster. + + There are three clustering translators: *unify*, *replicate*, and +*stripe*. The unify translator aggregates storage from many server +nodes. The replicate translator provides file replication. The stripe +translator allows a file to be spread across many server nodes. The +following sections look at each of these translators in detail. + +* Menu: + +* Unify:: +* Replicate:: +* Stripe:: + + +File: user-guide.info, Node: Unify, Next: Replicate, Up: Clustering Translators + +4.3.1 Unify +----------- + + type cluster/unify + + The unify translator presents a `unified' view of all its +sub-volumes. That is, it makes the union of all its sub-volumes appear +as a single volume. It is the unify translator that gives GlusterFS the +ability to access an arbitrarily large amount of storage. + + For unify to work correctly, certain invariants need to be +maintained across the entire network. These are: + + * The directory structure of all the sub-volumes must be identical. + + * A particular file can exist on only one of the sub-volumes. + Phrasing it in another way, a pathname such as + `/home/calvin/homework.txt') is unique across the entire cluster. + + + +Looking at the second requirement, you might wonder how one can +accomplish storing redundant copies of a file, if no file can exist +multiple times. To answer, we must remember that these invariants are +from _unify's perspective_. A translator such as replicate at a lower +level in the translator tree than unify may subvert this picture. + + The first invariant might seem quite tedious to ensure. We shall see +later that this is not so, since unify's _self-heal_ mechanism takes +care of maintaining it. + + The second invariant implies that unify needs some way to decide +which file goes where. Unify makes use of _scheduler_ modules for this +purpose. + + When a file needs to be created, unify's scheduler decides upon the +sub-volume to be used to store the file. There are many schedulers +available, each using a different algorithm and suitable for different +purposes. + + The various schedulers are described in detail in the sections that +follow. + +4.3.1.1 ALU +........... + + option scheduler alu + + ALU stands for "Adaptive Least Usage". It is the most advanced +scheduler available in GlusterFS. It balances the load across volumes +taking several factors in account. It adapts itself to changing I/O +patterns according to its configuration. When properly configured, it +can eliminate the need for regular tuning of the filesystem to keep +volume load nicely balanced. + + The ALU scheduler is composed of multiple least-usage +sub-schedulers. Each sub-scheduler keeps track of a certain type of +load, for each of the sub-volumes, getting statistics from the +sub-volumes themselves. The sub-schedulers are these: + + * disk-usage: The used and free disk space on the volume. + + * read-usage: The amount of reading done from this volume. + + * write-usage: The amount of writing done to this volume. + + * open-files-usage: The number of files currently open from this + volume. + + * disk-speed-usage: The speed at which the disks are spinning. This + is a constant value and therefore not very useful. + + The ALU scheduler needs to know which of these sub-schedulers to use, +and in which order to evaluate them. This is done through the `option +alu.order' configuration directive. + + Each sub-scheduler needs to know two things: when to kick in (the +entry-threshold), and how long to stay in control (the exit-threshold). +For example: when unifying three disks of 100GB, keeping an exact +balance of disk-usage is not necesary. Instead, there could be a 1GB +margin, which can be used to nicely balance other factors, such as +read-usage. The disk-usage scheduler can be told to kick in only when a +certain threshold of discrepancy is passed, such as 1GB. When it +assumes control under this condition, it will write all subsequent data +to the least-used volume. If it is doing so, it is unwise to stop right +after the values are below the entry-threshold again, since that would +make it very likely that the situation will occur again very soon. Such +a situation would cause the ALU to spend most of its time disk-usage +scheduling, which is unfair to the other sub-schedulers. The +exit-threshold therefore defines the amount of data that needs to be +written to the least-used disk, before control is relinquished again. + + In addition to the sub-schedulers, the ALU scheduler also has +"limits" options. These can stop the creation of new files on a volume +once values drop below a certain threshold. For example, setting +`option alu.limits.min-free-disk 5GB' will stop the scheduling of files +to volumes that have less than 5GB of free disk space, leaving the +files on that disk some room to grow. + + The actual values you assign to the thresholds for sub-schedulers and +limits depend on your situation. If you have fast-growing files, you'll +want to stop file-creation on a disk much earlier than when hardly any +of your files are growing. If you care less about disk-usage balance +than about read-usage balance, you'll want a bigger disk-usage +scheduler entry-threshold and a smaller read-usage scheduler +entry-threshold. + + For thresholds defining a size, values specifying "KB", "MB" and "GB" +are allowed. For example: `option alu.limits.min-free-disk 5GB'. + +`alu.order <order> * ("disk-usage:write-usage:read-usage:open-files-usage:disk-speed")' + +`alu.disk-usage.entry-threshold <size> (1GB)' + +`alu.disk-usage.exit-threshold <size> (512MB)' + +`alu.write-usage.entry-threshold <%> (25)' + +`alu.write-usage.exit-threshold <%> (5)' + +`alu.read-usage.entry-threshold <%> (25)' + +`alu.read-usage.exit-threshold <%> (5)' + +`alu.open-files-usage.entry-threshold <n> (1000)' + +`alu.open-files-usage.exit-threshold <n> (100)' + +`alu.limits.min-free-disk <%>' + +`alu.limits.max-open-files <n>' + +4.3.1.2 Round Robin (RR) +........................ + + option scheduler rr + + Round-Robin (RR) scheduler creates files in a round-robin fashion. +Each client will have its own round-robin loop. When your files are +mostly similar in size and I/O access pattern, this scheduler is a good +choice. RR scheduler checks for free disk space on the server before +scheduling, so you can know when to add another server node. The +default value of min-free-disk is 5% and is checked on file creation +calls, with atleast 10 seconds (by default) elapsing between two checks. + + Options: +`rr.limits.min-free-disk <%> (5)' + Minimum free disk space a node must have for RR to schedule a file + to it. + +`rr.refresh-interval <t> (10 seconds)' + Time between two successive free disk space checks. + +4.3.1.3 Random +.............. + + option scheduler random + + The random scheduler schedules file creation randomly among its +child nodes. Like the round-robin scheduler, it also checks for a +minimum amount of free disk space before scheduling a file to a node. + +`random.limits.min-free-disk <%> (5)' + Minimum free disk space a node must have for random to schedule a + file to it. + +`random.refresh-interval <t> (10 seconds)' + Time between two successive free disk space checks. + +4.3.1.4 NUFA +............ + + option scheduler nufa + + It is common in many GlusterFS computing environments for all +deployed machines to act as both servers and clients. For example, a +research lab may have 40 workstations each with its own storage. All of +these workstations might act as servers exporting a volume as well as +clients accessing the entire cluster's storage. In such a situation, +it makes sense to store locally created files on the local workstation +itself (assuming files are accessed most by the workstation that +created them). The Non-Uniform File Allocation (NUFA) scheduler +accomplishes that. + + NUFA gives the local system first priority for file creation over +other nodes. If the local volume does not have more free disk space +than a specified amount (5% by default) then NUFA schedules files among +the other child volumes in a round-robin fashion. + + NUFA is named after the similar strategy used for memory access, +NUMA(1). + +`nufa.limits.min-free-disk <%> (5)' + Minimum disk space that must be free (local or remote) for NUFA to + schedule a file to it. + +`nufa.refresh-interval <t> (10 seconds)' + Time between two successive free disk space checks. + +`nufa.local-volume-name <volume>' + The name of the volume corresponding to the local system. This + volume must be one of the children of the unify volume. This + option is mandatory. + +4.3.1.5 Namespace +................. + +Namespace volume needed because: - persistent inode numbers. - file +exists even when node is down. + + namespace files are simply touched. on every lookup it is checked. + +`namespace <volume> *' + Name of the namespace volume (which should be one of the unify + volume's children). + +`self-heal [on|off] (on)' + Enable/disable self-heal. Unless you know what you are doing, do + not disable self-heal. + +4.3.1.6 Self Heal +................. + +* When a 'lookup()/stat()' call is made on directory for the first +time, a self-heal call is made, which checks for the consistancy of its +child nodes. If an entry is present in storage node, but not in +namespace, that entry is created in namespace, and vica-versa. There is +an writedir() API introduced which is used for the same. It also checks +for permissions, and uid/gid consistencies. + + * This check is also done when an server goes down and comes up. + + * If one starts with an empty namespace export, but has data in +storage nodes, a 'find .>/dev/null' or 'ls -lR >/dev/null' should help +to build namespace in one shot. Even otherwise, namespace is built on +demand when a file is looked up for the first time. + + NOTE: There are some issues (Kernel 'Oops' msgs) seen with +fuse-2.6.3, when someone deletes namespace in backend, when glusterfs is +running. But with fuse-2.6.5, this issue is not there. + + ---------- Footnotes ---------- + + (1) Non-Uniform Memory Access: +<http://en.wikipedia.org/wiki/Non-Uniform_Memory_Access> + + +File: user-guide.info, Node: Replicate, Next: Stripe, Prev: Unify, Up: Clustering Translators + +4.3.2 Replicate (formerly AFR) +------------------------------ + + type cluster/replicate + + Replicate provides RAID-1 like functionality for GlusterFS. +Replicate replicates files and directories across the subvolumes. Hence +if Replicate has four subvolumes, there will be four copies of all +files and directories. Replicate provides high-availability, i.e., in +case one of the subvolumes go down (e. g. server crash, network +disconnection) Replicate will still service the requests using the +redundant copies. + + Replicate also provides self-heal functionality, i.e., in case the +crashed servers come up, the outdated files and directories will be +updated with the latest versions. Replicate uses extended attributes of +the backend file system to track the versioning of files and +directories and provide the self-heal feature. + + volume replicate-example + type cluster/replicate + subvolumes brick1 brick2 brick3 + end-volume + + This sample configuration will replicate all directories and files on +brick1, brick2 and brick3. + + All the read operations happen from the first alive child. If all the +three sub-volumes are up, reads will be done from brick1; if brick1 is +down read will be done from brick2. In case read() was being done on +brick1 and it goes down, replicate transparently falls back to brick2. + + The next release of GlusterFS will add the following features: + * Ability to specify the sub-volume from which read operations are + to be done (this will help users who have one of the sub-volumes + as a local storage volume). + + * Allow scheduling of read operations amongst the sub-volumes in a + round-robin fashion. + + The order of the subvolumes list should be same across all the +'replicate's as they will be used for locking purposes. + +4.3.2.1 Self Heal +................. + +Replicate has self-heal feature, which updates the outdated file and +directory copies by the most recent versions. For example consider the +following config: + + volume replicate-example + type cluster/replicate + subvolumes brick1 brick2 + end-volume + +4.3.2.2 File self-heal +...................... + +Now if we create a file foo.txt on replicate-example, the file will be +created on brick1 and brick2. The file will have two extended +attributes associated with it in the backend filesystem. One is +trusted.afr.createtime and the other is trusted.afr.version. The +trusted.afr.createtime xattr has the create time (in terms of seconds +since epoch) and trusted.afr.version is a number that is incremented +each time a file is modified. This increment happens during close +(incase any write was done before close). + + If brick1 goes down, we edit foo.txt the version gets incremented. +Now the brick1 comes back up, when we open() on foo.txt replicate will +check if their versions are same. If they are not same, the outdated +copy is replaced by the latest copy and its version is updated. After +the sync the open() proceeds in the usual manner and the application +calling open() can continue on its access to the file. + + If brick1 goes down, we delete foo.txt and create a file with the +same name again i.e foo.txt. Now brick1 comes back up, clearly there is +a chance that the version on brick1 being more than the version on +brick2, this is where createtime extended attribute helps in deciding +which the outdated copy is. Hence we need to consider both createtime +and version to decide on the latest copy. + + The version attribute is incremented during the close() call. Version +will not be incremented in case there was no write() done. In case the +fd that the close() gets was got by create() call, we also create the +createtime extended attribute. + +4.3.2.3 Directory self-heal +........................... + +Suppose brick1 goes down, we delete foo.txt, brick1 comes back up, now +we should not create foo.txt on brick2 but we should delete foo.txt on +brick1. We handle this situation by having the createtime and version +attribute on the directory similar to the file. when lookup() is done +on the directory, we compare the createtime/version attributes of the +copies and see which files needs to be deleted and delete those files +and update the extended attributes of the outdated directory copy. +Each time a directory is modified (a file or a subdirectory is created +or deleted inside the directory) and one of the subvols is down, we +increment the directory's version. + + lookup() is a call initiated by the kernel on a file or directory +just before any access to that file or directory. In glusterfs, by +default, lookup() will not be called in case it was called in the past +one second on that particular file or directory. + + The extended attributes can be seen in the backend filesystem using +the `getfattr' command. (`getfattr -n trusted.afr.version <file>') + +`debug [on|off] (off)' + +`self-heal [on|off] (on)' + +`replicate <pattern> (*:1)' + +`lock-node <child_volume> (first child is used by default)' + + +File: user-guide.info, Node: Stripe, Prev: Replicate, Up: Clustering Translators + +4.3.3 Stripe +------------ + + type cluster/stripe + + The stripe translator distributes the contents of a file over its +sub-volumes. It does this by creating a file equal in size to the +total size of the file on each of its sub-volumes. It then writes only +a part of the file to each sub-volume, leaving the rest of it empty. +These empty regions are called `holes' in Unix terminology. The holes +do not consume any disk space. + + The diagram below makes this clear. + + + +You can configure stripe so that only filenames matching a pattern are +striped. You can also configure the size of the data to be stored on +each sub-volume. + +`block-size <pattern>:<size> (*:0 no striping)' + Distribute files matching `<pattern>' over the sub-volumes, + storing at least `<size>' on each sub-volume. For example, + + option block-size *.mpg:1M + + distributes all files ending in `.mpg', storing at least 1 MB on + each sub-volume. + + Any number of `block-size' option lines may be present, specifying + different sizes for different file name patterns. + + +File: user-guide.info, Node: Performance Translators, Next: Features Translators, Prev: Clustering Translators, Up: Translators + +4.4 Performance Translators +=========================== + +* Menu: + +* Read Ahead:: +* Write Behind:: +* IO Threads:: +* IO Cache:: +* Booster:: + + +File: user-guide.info, Node: Read Ahead, Next: Write Behind, Up: Performance Translators + +4.4.1 Read Ahead +---------------- + + type performance/read-ahead + + The read-ahead translator pre-fetches data in advance on every read. +This benefits applications that mostly process files in sequential +order, since the next block of data will already be available by the +time the application is done with the current one. + + Additionally, the read-ahead translator also behaves as a +read-aggregator. Many small read operations are combined and issued as +fewer, larger read requests to the server. + + Read-ahead deals in "pages" as the unit of data fetched. The page +size is configurable, as is the "page count", which is the number of +pages that are pre-fetched. + + Read-ahead is best used with InfiniBand (using the ib-verbs +transport). On FastEthernet and Gigabit Ethernet networks, GlusterFS +can achieve the link-maximum throughput even without read-ahead, making +it quite superflous. + + Note that read-ahead only happens if the reads are perfectly +sequential. If your application accesses data in a random fashion, +using read-ahead might actually lead to a performance loss, since +read-ahead will pointlessly fetch pages which won't be used by the +application. + + Options: +`page-size <n> (256KB)' + The unit of data that is pre-fetched. + +`page-count <n> (2)' + The number of pages that are pre-fetched. + +`force-atime-update [on|off|yes|no] (off|no)' + Whether to force an access time (atime) update on the file on + every read. Without this, the atime will be slightly imprecise, as + it will reflect the time when the read-ahead translator read the + data, not when the application actually read it. + + +File: user-guide.info, Node: Write Behind, Next: IO Threads, Prev: Read Ahead, Up: Performance Translators + +4.4.2 Write Behind +------------------ + + type performance/write-behind + + The write-behind translator improves the latency of a write +operation. It does this by relegating the write operation to the +background and returning to the application even as the write is in +progress. Using the write-behind translator, successive write requests +can be pipelined. This mode of write-behind operation is best used on +the client side, to enable decreased write latency for the application. + + The write-behind translator can also aggregate write requests. If the +`aggregate-size' option is specified, then successive writes upto that +size are accumulated and written in a single operation. This mode of +operation is best used on the server side, as this will decrease the +disk's head movement when multiple files are being written to in +parallel. + + The `aggregate-size' option has a default value of 128KB. Although +this works well for most users, you should always experiment with +different values to determine the one that will deliver maximum +performance. This is because the performance of write-behind depends on +your interconnect, size of RAM, and the work load. + +`aggregate-size <n> (128KB)' + Amount of data to accumulate before doing a write + +`flush-behind [on|yes|off|no] (off|no)' + + +File: user-guide.info, Node: IO Threads, Next: IO Cache, Prev: Write Behind, Up: Performance Translators + +4.4.3 IO Threads +---------------- + + type performance/io-threads + + The IO threads translator is intended to increase the responsiveness +of the server to metadata operations by doing file I/O (read, write) in +a background thread. Since the GlusterFS server is single-threaded, +using the IO threads translator can significantly improve performance. +This translator is best used on the server side, loaded just below the +server protocol translator. + + IO threads operates by handing out read and write requests to a +separate thread. The total number of threads in existence at a time is +constant, and configurable. + +`thread-count <n> (1)' + Number of threads to use. + + +File: user-guide.info, Node: IO Cache, Next: Booster, Prev: IO Threads, Up: Performance Translators + +4.4.4 IO Cache +-------------- + + type performance/io-cache + + The IO cache translator caches data that has been read. This is +useful if many applications read the same data multiple times, and if +reads are much more frequent than writes (for example, IO caching may be +useful in a web hosting environment, where most clients will simply +read some files and only a few will write to them). + + The IO cache translator reads data from its child in `page-size' +chunks. It caches data upto `cache-size' bytes. The cache is +maintained as a prioritized least-recently-used (LRU) list, with +priorities determined by user-specified patterns to match filenames. + + When the IO cache translator detects a write operation, the cache +for that file is flushed. + + The IO cache translator periodically verifies the consistency of +cached data, using the modification times on the files. The +verification timeout is configurable. + +`page-size <n> (128KB)' + Size of a page. + +`cache-size (n) (32MB)' + Total amount of data to be cached. + +`force-revalidate-timeout <n> (1)' + Timeout to force a cache consistency verification, in seconds. + +`priority <pattern> (*:0)' + Filename patterns listed in order of priority. + + +File: user-guide.info, Node: Booster, Prev: IO Cache, Up: Performance Translators + +4.4.5 Booster +------------- + + type performance/booster + + The booster translator gives applications a faster path to +communicate read and write requests to GlusterFS. Normally, all +requests to GlusterFS from applications go through FUSE, as indicated +in *Note Filesystems in Userspace::. Using the booster translator in +conjunction with the GlusterFS booster shared library, an application +can bypass the FUSE path and send read/write requests directly to the +GlusterFS client process. + + The booster mechanism consists of two parts: the booster translator, +and the booster shared library. The booster translator is meant to be +loaded on the client side, usually at the root of the translator tree. +The booster shared library should be `LD_PRELOAD'ed with the +application. + + The booster translator when loaded opens a Unix domain socket and +listens for read/write requests on it. The booster shared library +intercepts read and write system calls and sends the requests to the +GlusterFS process directly using the Unix domain socket, bypassing FUSE. +This leads to superior performance. + + Once you've loaded the booster translator in your volume +specification file, you can start your application as: + + $ LD_PRELOAD=/usr/local/bin/glusterfs-booster.so your_app + + The booster translator accepts no options. + + +File: user-guide.info, Node: Features Translators, Next: Miscellaneous Translators, Prev: Performance Translators, Up: Translators + +4.5 Features Translators +======================== + +* Menu: + +* POSIX Locks:: +* Fixed ID:: + + +File: user-guide.info, Node: POSIX Locks, Next: Fixed ID, Up: Features Translators + +4.5.1 POSIX Locks +----------------- + + type features/posix-locks + + This translator provides storage independent POSIX record locking +support (`fcntl' locking). Typically you'll want to load this on the +server side, just above the POSIX storage translator. Using this +translator you can get both advisory locking and mandatory locking +support. It also handles `flock()' locks properly. + + Caveat: Consider a file that does not have its mandatory locking bits +(+setgid, -group execution) turned on. Assume that this file is now +opened by a process on a client that has the write-behind xlator +loaded. The write-behind xlator does not cache anything for files which +have mandatory locking enabled, to avoid incoherence. Let's say that +mandatory locking is now enabled on this file through another client. +The former client will not know about this change, and write-behind may +erroneously report a write as being successful when in fact it would +fail due to the region it is writing to being locked. + + There seems to be no easy way to fix this. To work around this +problem, it is recommended that you never enable the mandatory bits on +a file while it is open. + +`mandatory [on|off] (on)' + Turns mandatory locking on. + + +File: user-guide.info, Node: Fixed ID, Prev: POSIX Locks, Up: Features Translators + +4.5.2 Fixed ID +-------------- + + type features/fixed-id + + The fixed ID translator makes all filesystem requests from the client +to appear to be coming from a fixed, specified UID/GID, regardless of +which user actually initiated the request. + +`fixed-uid <n> [if not set, not used]' + The UID to send to the server + +`fixed-gid <n> [if not set, not used]' + The GID to send to the server + + +File: user-guide.info, Node: Miscellaneous Translators, Prev: Features Translators, Up: Translators + +4.6 Miscellaneous Translators +============================= + +* Menu: + +* ROT-13:: +* Trace:: + + +File: user-guide.info, Node: ROT-13, Next: Trace, Up: Miscellaneous Translators + +4.6.1 ROT-13 +------------ + + type encryption/rot-13 + + ROT-13 is a toy translator that can "encrypt" and "decrypt" file +contents using the ROT-13 algorithm. ROT-13 is a trivial algorithm that +rotates each alphabet by thirteen places. Thus, 'A' becomes 'N', 'B' +becomes 'O', and 'Z' becomes 'M'. + + It goes without saying that you shouldn't use this translator if you +need _real_ encryption (a future release of GlusterFS will have real +encryption translators). + +`encrypt-write [on|off] (on)' + Whether to encrypt on write + +`decrypt-read [on|off] (on)' + Whether to decrypt on read + + +File: user-guide.info, Node: Trace, Prev: ROT-13, Up: Miscellaneous Translators + +4.6.2 Trace +----------- + + type debug/trace + + The trace translator is intended for debugging purposes. When +loaded, it logs all the system calls received by the server or client +(wherever trace is loaded), their arguments, and the results. You must +use a GlusterFS log level of DEBUG (See *Note Running GlusterFS::) for +trace to work. + + Sample trace output (lines have been wrapped for readability): + 2007-10-30 00:08:58 D [trace.c:1579:trace_opendir] trace: callid: 68 + (*this=0x8059e40, loc=0x8091984 {path=/iozone3_283, inode=0x8091f00}, + fd=0x8091d50) + + 2007-10-30 00:08:58 D [trace.c:630:trace_opendir_cbk] trace: + (*this=0x8059e40, op_ret=4, op_errno=1, fd=0x8091d50) + + 2007-10-30 00:08:58 D [trace.c:1602:trace_readdir] trace: callid: 69 + (*this=0x8059e40, size=4096, offset=0 fd=0x8091d50) + + 2007-10-30 00:08:58 D [trace.c:215:trace_readdir_cbk] trace: + (*this=0x8059e40, op_ret=0, op_errno=0, count=4) + + 2007-10-30 00:08:58 D [trace.c:1624:trace_closedir] trace: callid: 71 + (*this=0x8059e40, *fd=0x8091d50) + + 2007-10-30 00:08:58 D [trace.c:809:trace_closedir_cbk] trace: + (*this=0x8059e40, op_ret=0, op_errno=1) + + +File: user-guide.info, Node: Usage Scenarios, Next: Troubleshooting, Prev: Translators, Up: Top + +5 Usage Scenarios +***************** + +5.1 Advanced Striping +===================== + +This section is based on the Advanced Striping tutorial written by +Anand Avati on the GlusterFS wiki (1). + +5.1.1 Mixed Storage Requirements +-------------------------------- + +There are two ways of scheduling the I/O. One at file level (using +unify translator) and other at block level (using stripe translator). +Striped I/O is good for files that are potentially large and require +high parallel throughput (for example, a single file of 400GB being +accessed by 100s and 1000s of systems simultaneously and randomly). For +most of the cases, file level scheduling works best. + + In the real world, it is desirable to mix file level and block level +scheduling on a single storage volume. Alternatively users can choose +to have two separate volumes and hence two mount points, but the +applications may demand a single storage system to host both. + + This document explains how to mix file level scheduling with stripe. + +5.1.2 Configuration Brief +------------------------- + +This setup demonstrates how users can configure unify translator with +appropriate I/O scheduler for file level scheduling and strip for only +matching patterns. This way, GlusterFS chooses appropriate I/O profile +and knows how to efficiently handle both the types of data. + + A simple technique to achieve this effect is to create a stripe set +of unify and stripe blocks, where unify is the first sub-volume. Files +that do not match the stripe policy passed on to first unify sub-volume +and inturn scheduled arcoss the cluster using its file level I/O +scheduler. + + 5.1.3 Preparing GlusterFS Envoronment +------------------------------------- + +Create the directories /export/namespace, /export/unify and +/export/stripe on all the storage bricks. + + Place the following server and client volume spec file under +/etc/glusterfs (or appropriate installed path) and replace the IP +addresses / access control fields to match your environment. + + ## file: /etc/glusterfs/glusterfsd.vol + volume posix-unify + type storage/posix + option directory /export/for-unify + end-volume + + volume posix-stripe + type storage/posix + option directory /export/for-stripe + end-volume + + volume posix-namespace + type storage/posix + option directory /export/for-namespace + end-volume + + volume server + type protocol/server + option transport-type tcp + option auth.addr.posix-unify.allow 192.168.1.* + option auth.addr.posix-stripe.allow 192.168.1.* + option auth.addr.posix-namespace.allow 192.168.1.* + subvolumes posix-unify posix-stripe posix-namespace + end-volume + + ## file: /etc/glusterfs/glusterfs.vol + volume client-namespace + type protocol/client + option transport-type tcp + option remote-host 192.168.1.1 + option remote-subvolume posix-namespace + end-volume + + volume client-unify-1 + type protocol/client + option transport-type tcp + option remote-host 192.168.1.1 + option remote-subvolume posix-unify + end-volume + + volume client-unify-2 + type protocol/client + option transport-type tcp + option remote-host 192.168.1.2 + option remote-subvolume posix-unify + end-volume + + volume client-unify-3 + type protocol/client + option transport-type tcp + option remote-host 192.168.1.3 + option remote-subvolume posix-unify + end-volume + + volume client-unify-4 + type protocol/client + option transport-type tcp + option remote-host 192.168.1.4 + option remote-subvolume posix-unify + end-volume + + volume client-stripe-1 + type protocol/client + option transport-type tcp + option remote-host 192.168.1.1 + option remote-subvolume posix-stripe + end-volume + + volume client-stripe-2 + type protocol/client + option transport-type tcp + option remote-host 192.168.1.2 + option remote-subvolume posix-stripe + end-volume + + volume client-stripe-3 + type protocol/client + option transport-type tcp + option remote-host 192.168.1.3 + option remote-subvolume posix-stripe + end-volume + + volume client-stripe-4 + type protocol/client + option transport-type tcp + option remote-host 192.168.1.4 + option remote-subvolume posix-stripe + end-volume + + volume unify + type cluster/unify + option scheduler rr + subvolumes cluster-unify-1 cluster-unify-2 cluster-unify-3 cluster-unify-4 + end-volume + + volume stripe + type cluster/stripe + option block-size *.img:2MB # All files ending with .img are striped with 2MB stripe block size. + subvolumes unify cluster-stripe-1 cluster-stripe-2 cluster-stripe-3 cluster-stripe-4 + end-volume + + Bring up the Storage + + Starting GlusterFS Server: If you have installed through binary +package, you can start the service through init.d startup script. If +not: + + [root@server]# glusterfsd + + Mounting GlusterFS Volumes: + + [root@client]# glusterfs -s [BRICK-IP-ADDRESS] /mnt/cluster + + Improving upon this Setup + + Infiniband Verbs RDMA transport is much faster than TCP/IP GigE +transport. + + Use of performance translators such as read-ahead, write-behind, +io-cache, io-threads, booster is recommended. + + Replace round-robin (rr) scheduler with ALU to handle more dynamic +storage environments. + + ---------- Footnotes ---------- + + (1) +http://gluster.org/docs/index.php/Mixing_Striped_and_Regular_Files + + +File: user-guide.info, Node: Troubleshooting, Next: GNU Free Documentation Licence, Prev: Usage Scenarios, Up: Top + +6 Troubleshooting +***************** + +This chapter is a general troubleshooting guide to GlusterFS. It lists +common GlusterFS server and client error messages, debugging hints, and +concludes with the suggested procedure to report bugs in GlusterFS. + +6.1 GlusterFS error messages +============================ + +6.1.1 Server errors +------------------- + + glusterfsd: FATAL: could not open specfile: + '/etc/glusterfs/glusterfsd.vol' + + The GlusterFS server expects the volume specification file to be at +`/etc/glusterfs/glusterfsd.vol'. The example specification file will be +installed as `/etc/glusterfs/glusterfsd.vol.sample'. You need to edit +it and rename it, or provide a different specification file using the +`--spec-file' command line option (See *Note Server::). + + gf_log_init: failed to open logfile "/usr/var/log/glusterfs/glusterfsd.log" + (Permission denied) + + You don't have permission to create files in the +`/usr/var/log/glusterfs' directory. Make sure you are running GlusterFS +as root. Alternatively, specify a different path for the log file using +the `--log-file' option (See *Note Server::). + +6.1.2 Client errors +------------------- + + fusermount: failed to access mountpoint /mnt: + Transport endpoint is not connected + + A previous failed (or hung) mount of GlusterFS is preventing it from +being mounted again in the same location. The fix is to do: + + # umount /mnt + + and try mounting again. + + *"Transport endpoint is not connected".* + + If you get this error when you try a command such as `ls' or `cat', +it means the GlusterFS mount did not succeed. Try running GlusterFS in +`DEBUG' logging level and study the log messages to discover the cause. + + *"Connect to server failed", "SERVER-ADDRESS: Connection refused".* + + GluserFS Server is not running or dead. Check your network +connections and firewall settings. To check if the server is reachable, +try: + + telnet IP-ADDRESS 6996 + + If the server is accessible, your `telnet' command should connect and +block. If not you will see an error message such as `telnet: Unable to +connect to remote host: Connection refused'. 6996 is the default +GlusterFS port. If you have changed it, then use the corresponding port +instead. + + gf_log_init: failed to open logfile "/usr/var/log/glusterfs/glusterfs.log" + (Permission denied) + + You don't have permission to create files in the +`/usr/var/log/glusterfs' directory. Make sure you are running GlusterFS +as root. Alternatively, specify a different path for the log file using +the `--log-file' option (See *Note Client::). + +6.2 FUSE error messages +======================= + +`modprobe fuse' fails with: "Unknown symbol in module, or unknown +parameter". + + If you are using fuse-2.6.x on Redhat Enterprise Linux Work Station 4 +and Advanced Server 4 with 2.6.9-42.ELlargesmp, 2.6.9-42.ELsmp, +2.6.9-42.EL kernels and get this error while loading FUSE kernel +module, you need to apply the following patch. + + For fuse-2.6.2: + +<http://ftp.zresearch.com/pub/gluster/glusterfs/fuse/fuse-2.6.2-rhel-build.patch> + + For fuse-2.6.3: + +<http://ftp.zresearch.com/pub/gluster/glusterfs/fuse/fuse-2.6.3-rhel-build.patch> + +6.3 AppArmour and GlusterFS +=========================== + +Under OpenSuSE GNU/Linux, the AppArmour security feature does not allow +GlusterFS to create temporary files or network socket connections even +while running as root. You will see error messages like `Unable to open +log file: Operation not permitted' or `Connection refused'. Disabling +AppArmour using YaST or properly configuring AppArmour to recognize +`glusterfsd' or `glusterfs'/`fusermount' should solve the problem. + +6.4 Reporting a bug +=================== + +If you encounter a bug in GlusterFS, please follow the below guidelines +when you report it to the mailing list. Be sure to report it! User +feedback is crucial to the health of the project and we value it highly. + +6.4.1 General instructions +-------------------------- + +When running GlusterFS in a non-production environment, be sure to +build it with the following command: + + $ make CFLAGS='-g -O0 -DDEBUG' + + This includes debugging information which will be helpful in getting +backtraces (see below) and also disable optimization. Enabling +optimization can result in incorrect line numbers being reported to gdb. + +6.4.2 Volume specification files +-------------------------------- + +Attach all relevant server and client spec files you were using when +you encountered the bug. Also tell us details of your setup, i.e., how +many clients and how many servers. + +6.4.3 Log files +--------------- + +Set the loglevel of your client and server programs to DEBUG (by +passing the -L DEBUG option) and attach the log files with your bug +report. Obviously, if only the client is failing (for example), you +only need to send us the client log file. + +6.4.4 Backtrace +--------------- + +If GlusterFS has encountered a segmentation fault or has crashed for +some other reason, include the backtrace with the bug report. You can +get the backtrace using the following procedure. + + Run the GlusterFS client or server inside gdb. + + $ gdb ./glusterfs + (gdb) set args -f client.spec -N -l/path/to/log/file -LDEBUG /mnt/point + (gdb) run + + Now when the process segfaults, you can get the backtrace by typing: + + (gdb) bt + + If the GlusterFS process has crashed and dumped a core file (you can +find this in / if running as a daemon and in the current directory +otherwise), you can do: + + $ gdb /path/to/glusterfs /path/to/core.<pid> + + and then get the backtrace. + + If the GlusterFS server or client seems to be hung, then you can get +the backtrace by attaching gdb to the process. First get the `PID' of +the process (using ps), and then do: + + $ gdb ./glusterfs <pid> + + Press Ctrl-C to interrupt the process and then generate the +backtrace. + +6.4.5 Reproducing the bug +------------------------- + +If the bug is reproducible, please include the steps necessary to do +so. If the bug is not reproducible, send us the bug report anyway. + +6.4.6 Other information +----------------------- + +If you think it is relevant, send us also the version of FUSE you're +using, the kernel version, platform. + + +File: user-guide.info, Node: GNU Free Documentation Licence, Next: Index, Prev: Troubleshooting, Up: Top + +Appendix A GNU Free Documentation Licence +***************************************** + + Version 1.2, November 2002 + + Copyright (C) 2000,2001,2002 Free Software Foundation, Inc. + 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA + + Everyone is permitted to copy and distribute verbatim copies + of this license document, but changing it is not allowed. + + 0. PREAMBLE + + The purpose of this License is to make a manual, textbook, or other + functional and useful document "free" in the sense of freedom: to + assure everyone the effective freedom to copy and redistribute it, + with or without modifying it, either commercially or + noncommercially. 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A copy of the license is included in the section entitled ``GNU + Free Documentation License''. + + If you have Invariant Sections, Front-Cover Texts and Back-Cover +Texts, replace the "with...Texts." line with this: + + with the Invariant Sections being LIST THEIR TITLES, with + the Front-Cover Texts being LIST, and with the Back-Cover Texts + being LIST. + + If you have Invariant Sections without Cover Texts, or some other +combination of the three, merge those two alternatives to suit the +situation. + + If your document contains nontrivial examples of program code, we +recommend releasing these examples in parallel under your choice of +free software license, such as the GNU General Public License, to +permit their use in free software. + + +File: user-guide.info, Node: Index, Prev: GNU Free Documentation Licence, Up: Top + +Index +***** + + +* Menu: + +* alu (scheduler): Unify. (line 49) +* AppArmour: Troubleshooting. (line 96) +* arch: Getting GlusterFS. (line 6) +* booster: Booster. (line 6) +* commercial support: Introduction. (line 36) +* DNS round robin: Transport modules. (line 29) +* fcntl: POSIX Locks. (line 6) +* FDL, GNU Free Documentation License: GNU Free Documentation Licence. + (line 6) +* fixed-id (translator): Fixed ID. (line 6) +* GlusterFS client: Client. (line 6) +* GlusterFS mailing list: Introduction. (line 28) +* GlusterFS server: Server. (line 6) +* infiniband transport: Transport modules. (line 58) +* InfiniBand, installation: Pre requisites. (line 51) +* io-cache (translator): IO Cache. (line 6) +* io-threads (translator): IO Threads. (line 6) +* IRC channel, #gluster: Introduction. (line 31) +* libibverbs: Pre requisites. (line 51) +* namespace: Unify. (line 207) +* nufa (scheduler): Unify. (line 175) +* OpenSuSE: Troubleshooting. (line 96) +* posix-locks (translator): POSIX Locks. (line 6) +* random (scheduler): Unify. (line 159) +* read-ahead (translator): Read Ahead. (line 6) +* record locking: POSIX Locks. (line 6) +* Redhat Enterprise Linux: Troubleshooting. (line 78) +* Replicate: Replicate. (line 6) +* rot-13 (translator): ROT-13. (line 6) +* rr (scheduler): Unify. (line 138) +* scheduler (unify): Unify. (line 6) +* self heal (replicate): Replicate. (line 46) +* self heal (unify): Unify. (line 223) +* stripe (translator): Stripe. (line 6) +* trace (translator): Trace. (line 6) +* unify (translator): Unify. (line 6) +* unify invariants: Unify. (line 16) +* write-behind (translator): Write Behind. (line 6) +* Z Research, Inc.: Introduction. (line 36) + + + +Tag Table: +Node: Top703 +Node: Acknowledgements2303 +Node: Introduction3213 +Node: Installation and Invocation4648 +Node: Pre requisites4932 +Node: Getting GlusterFS7022 +Ref: Getting GlusterFS-Footnote-17808 +Node: Building7856 +Node: Running GlusterFS9558 +Node: Server9769 +Node: Client11357 +Node: A Tutorial Introduction13563 +Node: Concepts17100 +Node: Filesystems in Userspace17315 +Node: Translator18456 +Node: Volume specification file21159 +Node: Translators23631 +Node: Storage Translators24200 +Ref: Storage Translators-Footnote-125007 +Node: POSIX25141 +Node: BDB25764 +Node: Client and Server Translators26821 +Node: Transport modules27297 +Node: Client protocol31444 +Node: Server protocol32383 +Node: Clustering Translators33372 +Node: Unify34259 +Ref: Unify-Footnote-143858 +Node: Replicate43950 +Node: Stripe49005 +Node: Performance Translators50163 +Node: Read Ahead50437 +Node: Write Behind52169 +Node: IO Threads53578 +Node: IO Cache54366 +Node: Booster55690 +Node: Features Translators57104 +Node: POSIX Locks57332 +Node: Fixed ID58649 +Node: Miscellaneous Translators59135 +Node: ROT-1359333 +Node: Trace60012 +Node: Usage Scenarios61281 +Ref: Usage Scenarios-Footnote-167214 +Node: Troubleshooting67289 +Node: GNU Free Documentation Licence73637 +Node: Index96086 + +End Tag Table |