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diff --git a/doc/legacy/user-guide.texi b/doc/legacy/user-guide.texi deleted file mode 100644 index 31ff9cf304e..00000000000 --- a/doc/legacy/user-guide.texi +++ /dev/null @@ -1,2246 +0,0 @@ -\input texinfo -@setfilename user-guide.info -@settitle GlusterFS 2.0 User Guide -@afourpaper - -@direntry -* GlusterFS: (user-guide). GlusterFS distributed filesystem user guide -@end direntry - -@copying -This is the user manual for GlusterFS 2.0. - -Copyright @copyright{} 2007-2011 @email{@b{Gluster}} , Inc. Permission is granted to -copy, distribute and/or modify this document under the terms of the -@acronym{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 ``@acronym{GNU} Free -Documentation License''. -@end copying - -@titlepage -@title GlusterFS 2.0 User Guide [DRAFT] -@subtitle January 15, 2008 -@author http://gluster.org/core-team.php -@author @email{@b{Gluster}} -@page -@vskip 0pt plus 1filll -@insertcopying -@end titlepage - -@c Info stuff -@ifnottex -@node Top -@top GlusterFS 2.0 User Guide - -@insertcopying -@menu -* Acknowledgements:: -* Introduction:: -* Installation and Invocation:: -* Concepts:: -* Translators:: -* Usage Scenarios:: -* Troubleshooting:: -* GNU Free Documentation Licence:: -* Index:: - -@detailmenu - --- 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:: - -@end detailmenu -@end menu - -@end ifnottex -@c Info stuff end - -@contents - -@node Acknowledgements -@unnumbered 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. -@flushright -http://gluster.org/core-team.php (@email{list-hacking@@gluster.com}) -@email{@b{Gluster}} -@end flushright - -@node Introduction -@chapter 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 - -@itemize @bullet -@item Scalability: A distributed filesystem allows us to store more data than what can be stored on a single machine. - -@item Redundancy: We might want to replicate crucial data on to several machines. - -@item Uniform access: One can mount a remote volume (for example your home directory) from any machine and access the same data. -@end itemize - -@section Contacting us -You can reach us through the mailing list @strong{gluster-devel} -(@email{gluster-devel@@nongnu.org}). -@cindex GlusterFS mailing list - -You can also find many of the developers on @acronym{IRC}, on the @code{#gluster} -channel on Freenode (@indicateurl{irc.freenode.net}). -@cindex IRC channel, #gluster - -The GlusterFS documentation wiki is also useful: @* -@indicateurl{http://gluster.org/docs/index.php/GlusterFS} - -For commercial support, you can contact @email{@b{Gluster}} at: -@cindex commercial support -@cindex Gluster, Inc. - -@display -3194 Winding Vista Common -Fremont, CA 94539 -USA. - -Phone: +1 (510) 354 6801 -Toll free: +1 (888) 813 6309 -Fax: +1 (510) 372 0604 -@end display - -You can also email us at @email{support@@gluster.com}. - -@node Installation and Invocation -@chapter Installation and Invocation - -@menu -* Pre requisites:: -* Getting GlusterFS:: -* Building:: -* Running GlusterFS:: -* A Tutorial Introduction:: -@end menu - -@node Pre requisites -@section Pre requisites - -Before installing GlusterFS make sure you have the -following components installed. - -@subsection @acronym{FUSE} -GlusterFS has now built-in support for the @acronym{FUSE} protocol. -You need a kernel with @acronym{FUSE} support to mount GlusterFS. -You do not need the @acronym{FUSE} package (library and utilities), -but be aware of the following issues: - -@itemize -@item If you want unprivileged users to be able to mount GlusterFS filesystems, -you need a recent version of the @command{fusermount} utility. You already have -it if you have @acronym{FUSE} version 2.7.0 or higher installed; if that's not -the case, one will be compiled along with GlusterFS if you pass -@command{--enable-fusermount} to the @command{configure} script. @item You -need to ensure @acronym{FUSE} support is configured properly on your system. In -details: -@itemize -@item If your kernel has @acronym{FUSE} as a loadable module, make sure it's -loaded. -@item Create @command{/dev/fuse} (major 10, minor 229) either by means of udev -rules or by hand. -@item Optionally, if you want runtime control over your @acronym{FUSE} mounts, -mount the fusectl auxiliary filesystem: - -@example -# mount -t fusectl none /sys/fs/fuse/connections -@end example -@end itemize - -The @acronym{FUSE} packages shipped by the various distributions usually take care -about these things, so the easiest way to get the above tasks handled is still -installing the @acronym{FUSE} package(s). -@end itemize - -To get the best performance from GlusterFS,it is recommended that you use -our patched version of the @acronym{FUSE} kernel module. See Patched FUSE for details. - -@subsection Patched FUSE - -The GlusterFS project maintains a patched version of @acronym{FUSE} meant to be used -with GlusterFS. The patches increase GlusterFS performance. It is recommended that -all users use the patched @acronym{FUSE}. - -The patched @acronym{FUSE} tarball can be downloaded from: - -@indicateurl{ftp://ftp.gluster.com/pub/gluster/glusterfs/fuse/} - -The specific changes made to @acronym{FUSE} are: - -@itemize -@item The communication channel size between @acronym{FUSE} kernel module and GlusterFS has been increased to 1MB, permitting large reads and writes to be sent in bigger chunks. - -@item The kernel's read-ahead boundary has been extended up to 1MB. - -@item Block size returned in the @command{stat()}/@command{fstat()} calls tuned to 1MB, to make cp and similar commands perform I/O using that block size. - -@item @command{flock()} locking support has been added (although some rework in GlusterFS is needed for perfect compliance). -@end itemize - -@subsection libibverbs (optional) -@cindex InfiniBand, installation -@cindex libibverbs -This is only needed if you want GlusterFS to use InfiniBand as the -interconnect mechanism between server and client. You can get it from: - -@indicateurl{http://www.openfabrics.org/downloads.htm}. - -@subsection 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. - -@node Getting GlusterFS -@section Getting GlusterFS -@cindex arch -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: @indicateurl{http://gluster.org/download.php}. - -If you want the bleeding edge development source, you can get them -from the Git -@footnote{@indicateurl{http://git-scm.com}} -repository. First you must install Git itself. Then -you can check out the source - -@example -$ git clone git://git.sv.gnu.org/gluster.git glusterfs -@end example - -@node Building -@section Building -You can skip this section if you're installing from @acronym{RPM}s -or @acronym{DEB}s. - -GlusterFS uses the Autotools mechanism to build. As such, the procedure -is straight-forward. First, change into the GlusterFS source directory. - -@example -$ cd glusterfs-<version> -@end example - -If you checked out the source from the Arch repository, you'll need -to run @command{./autogen.sh} first. Note that you'll need to have -Autoconf and Automake installed for this. - -Run @command{configure}. - -@example -$ ./configure -@end example - -The configure script accepts the following options: - -@cartouche -@table @code - -@item --disable-ibverbs -Disable the InfiniBand transport mechanism. - -@item --disable-fuse-client -Disable the @acronym{FUSE} client. - -@item --disable-server -Disable building of the GlusterFS server. - -@item --disable-bdb -Disable building of Berkeley DB based storage translator. - -@item --disable-mod_glusterfs -Disable building of Apache/lighttpd glusterfs plugins. - -@item --disable-epoll -Use poll instead of epoll. - -@item --disable-libglusterfsclient -Disable building of libglusterfsclient - -@item --enable-fusermount -Build fusermount - -@end table -@end cartouche - -Build and install GlusterFS. - -@example -# make install -@end example - -The binaries (@command{glusterfsd} and @command{glusterfs}) will be by -default installed in @command{/usr/local/sbin/}. Translator, -scheduler, and transport shared libraries will be installed in -@command{/usr/local/lib/glusterfs/<version>/}. Sample volume -specification files will be in @command{/usr/local/etc/glusterfs/}. -This document itself can be found in -@command{/usr/local/share/doc/glusterfs/}. If you passed the @command{--prefix} -argument to the configure script, then replace @command{/usr/local} in the preceding -paths with the prefix. - -@node Running GlusterFS -@section Running GlusterFS - -@menu -* Server:: -* Client:: -@end menu - -@node Server -@subsection Server -@cindex GlusterFS server - -The GlusterFS server is necessary to export storage volumes to remote clients -(See @ref{Server protocol} for more info). This section documents the invocation -of the GlusterFS server program and all the command-line options accepted by it. - -@cartouche -@table @code -Basic Options -@item -f, --volfile=<path> - Use the volume file as the volume specification. - -@item -s, --volfile-server=<hostname> - Server to get volume file from. This option overrides --volfile option. - -@item -l, --log-file=<path> - Specify the path for the log file. - -@item -L, --log-level=<level> - Set the log level for the server. Log level should be one of @acronym{DEBUG}, -@acronym{WARNING}, @acronym{ERROR}, @acronym{CRITICAL}, or @acronym{NONE}. - -Advanced Options -@item --debug - Run in debug mode. This option sets --no-daemon, --log-level to DEBUG and - --log-file to console. - -@item -N, --no-daemon - Run glusterfsd as a foreground process. - -@item -p, --pid-file=<path> - Path for the @acronym{PID} file. - -@item --volfile-id=<key> - 'key' of the volfile to be fetched from server. - -@item --volfile-server-port=<port-number> - Listening port number of volfile server. - -@item --volfile-server-transport=[tcp|ib-verbs] - Transport type to get volfile from server. [default: @command{tcp}] - -@item --xlator-options=<volume-name.option=value> - Add/override a translator option for a volume with specified value. - -Miscellaneous Options -@item -?, --help - Show this help text. - -@item --usage - Display a short usage message. - -@item -V, --version - Show version information. -@end table -@end cartouche - -@node Client -@subsection Client -@cindex GlusterFS client - -The GlusterFS client process is necessary to access remote storage volumes and -mount them locally using @acronym{FUSE}. This section documents the invocation of the -client process and all its command-line arguments. - -@example - # glusterfs [options] <mountpoint> -@end example - -The @command{mountpoint} is the directory where you want the GlusterFS -filesystem to appear. Example: - -@example - # glusterfs -f /usr/local/etc/glusterfs-client.vol /mnt -@end example - -The command-line options are detailed below. - -@tex -\vfill -@end tex -@page - -@cartouche -@table @code - -Basic Options -@item -f, --volfile=<path> - Use the volume file as the volume specification. - -@item -s, --volfile-server=<hostname> - Server to get volume file from. This option overrides --volfile option. - -@item -l, --log-file=<path> - Specify the path for the log file. - -@item -L, --log-level=<level> - Set the log level for the server. Log level should be one of @acronym{DEBUG}, -@acronym{WARNING}, @acronym{ERROR}, @acronym{CRITICAL}, or @acronym{NONE}. - -Advanced Options -@item --debug - Run in debug mode. This option sets --no-daemon, --log-level to DEBUG and - --log-file to console. - -@item -N, --no-daemon - Run @command{glusterfs} as a foreground process. - -@item -p, --pid-file=<path> - Path for the @acronym{PID} file. - -@item --volfile-id=<key> - 'key' of the volfile to be fetched from server. - -@item --volfile-server-port=<port-number> - Listening port number of volfile server. - -@item --volfile-server-transport=[tcp|ib-verbs] - Transport type to get volfile from server. [default: @command{tcp}] - -@item --xlator-options=<volume-name.option=value> - Add/override a translator option for a volume with specified value. - -@item --volume-name=<volume name> - Volume name in client spec to use. Defaults to the root volume. - -@acronym{FUSE} Options -@item --attribute-timeout=<n> - Attribute timeout for inodes in the kernel, in seconds. Defaults to 1 second. - -@item --disable-direct-io-mode - Disable direct @acronym{I/O} mode in @acronym{FUSE} kernel module. This is set - automatically if kernel supports big writes (>= 2.6.26). - -@item -e, --entry-timeout=<n> - Entry timeout for directory entries in the kernel, in seconds. - Defaults to 1 second. - -Missellaneous Options -@item -?, --help - Show this help information. - -@item -V, --version - Show version information. -@end table -@end cartouche - -@node A Tutorial Introduction -@section 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 @emph{server} and -@emph{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: - -@example -[root@@server]# -@end example - -Our goal is to make a directory on the @emph{server} (say, @command{/export}) -accessible to the @emph{client}. - -First of all, get GlusterFS installed on both the machines, as described in the -previous sections. Make sure you have the @acronym{FUSE} kernel module loaded. You -can ensure this by running: - -@example -[root@@server]# modprobe fuse -@end example - -Before we can run the GlusterFS client or server programs, we need to write -two files called @emph{volume specifications} (equivalently referred to as @emph{volfiles}). -The volfile describes the @emph{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 @command{/etc/export} file. - -On the server, create a text file somewhere (we'll assume the path -@command{/tmp/glusterfsd.vol}) with the following contents. - -@cartouche -@example -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 -@end example -@end cartouche - -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 -@command{/export} directory. The second section defines options for the translator -which will make the storage volume accessible remotely. It specifies @command{colon-o} as -a subvolume. This defines the @emph{translator tree}, about which more will be said -in the next chapter. The two options specify that the @acronym{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 @acronym{IP} address at all. If you wanted to -restrict access to this server to only your subnet for example, you'd specify -something like @command{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 @command{/tmp/glusterfs-client.vol}). Replace -@emph{server-ip-address} with the @acronym{IP} address of your server machine. If you -are doing all this on a single machine, use @command{127.0.0.1}. - -@cartouche -@example -volume client - type protocol/client - option transport-type tcp - option remote-host @emph{server-ip-address} - option remote-subvolume colon-o -end-volume -@end example -@end cartouche - -Now we need to start both the server and client programs. To start the server: - -@example -[root@@server]# glusterfsd -f /tmp/glusterfs-server.vol -@end example - -To start the client: - -@example -[root@@client]# glusterfs -f /tmp/glusterfs-client.vol /mnt/glusterfs -@end example - -You should now be able to see the files under the server's @command{/export} directory -in the @command{/mnt/glusterfs} directory on the client. That's it; GlusterFS is now -working as a network file system. - -@node Concepts -@chapter Concepts - -@menu -* Filesystems in Userspace:: -* Translator:: -* Volume specification file:: -@end menu - -@node Filesystems in Userspace -@section Filesystems in Userspace - -A filesystem is usually implemented in kernel space. Kernel space -development is much harder than userspace development. @acronym{FUSE} -is a kernel module/library that allows us to write a filesystem -completely in userspace. - -@acronym{FUSE} consists of a kernel module which interacts with the userspace -implementation using a device file @code{/dev/fuse}. When a process -makes a syscall on a @acronym{FUSE} filesystem, @acronym{VFS} hands the request to the -@acronym{FUSE} module, which writes the request to @code{/dev/fuse}. The -userspace implementation polls @code{/dev/fuse}, and when a request arrives, -processes it and writes the result back to @code{/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 @acronym{POSIX} filesystem. - -@center @image{fuse,44pc,,,.pdf} -@center Fig 1. Control flow in GlusterFS - -@node Translator -@section Translator - -The @emph{translator} is the most important concept in GlusterFS. In -fact, GlusterFS is nothing but a collection of translators working -together, forming a translator @emph{tree}. - -The idea of a translator is perhaps best understood using an -analogy. Consider the @acronym{VFS} in the Linux kernel. The -@acronym{VFS} abstracts the various filesystem implementations (such -as @acronym{EXT3}, ReiserFS, @acronym{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: -@command{/}, which is an @acronym{EXT3} partition, and @command{/usr}, -which is a ReiserFS partition. Now if an application wants to open a -file called, say, @command{/etc/fstab}, then the kernel will -internally pass the request to the @acronym{EXT3} implementation. If -on the other hand, an application wants to read a file called -@command{/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 @acronym{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 (@command{.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? - -@tex -\vfill -@end tex -@page - -@center @image{xlator,44pc,,,.pdf} -@center 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, @command{10.0.0.1}, can access -the aggregated storage of the filesystems on the server machines @command{10.0.0.2}, -@command{10.0.0.3}, and @command{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. - -@node Volume specification file -@section 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: - -@cartouche -@example -@strong{volume} @emph{volume-name} - @strong{type} @emph{translator-name} - @strong{option} @emph{option-name} @emph{option-value} - @dots{} - @strong{subvolumes} @emph{subvolume1} @emph{subvolume2} @dots{} -@strong{end-volume} -@end example - -@dots{} -@end cartouche - -@table @asis -@item @emph{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''. - -@item @emph{translator-name} - Name of one of the available translators. Example: @command{protocol/client}, -@command{cluster/unify}. - -@item @emph{option-name} - Name of a valid option for the translator. - -@item @emph{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. - -@item @emph{subvolume1}, @emph{subvolume2}, @dots{} - Volume names of sub-volumes. The sub-volumes must already have been defined earlier -in the file. -@end table - -There are a few rules you must follow when writing a volume specification file: - -@itemize -@item Everything following a `@command{#}' is considered a comment and is ignored. Blank lines are also ignored. -@item All names and keywords are case-sensitive. -@item The order of options inside a volume definition does not matter. -@item An option value may not span multiple lines. -@item If an option is not specified, it will assume its default value. -@item 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. -@end itemize - -A simple example volume specification file is shown below: - -@cartouche -@example -# 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 -@end example -@end cartouche - -@node Translators -@chapter Translators - -@menu -* Storage Translators:: -* Client and Server Translators:: -* Clustering Translators:: -* Performance Translators:: -* Features Translators:: -* Miscellaneous Translators:: -@end menu - -This chapter documents all the available GlusterFS translators in detail. -Each translator section will show its name (for example, @command{cluster/unify}), -briefly describe its purpose and workings, and list every option accepted by -that translator and their meaning. - -@node Storage Translators -@section Storage Translators - -The storage translators form the ``backend'' for GlusterFS. Currently, -the only available storage translator is the @acronym{POSIX} -translator, which stores files on a normal @acronym{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 @acronym{API}. The S3 translator will allow you to access -the storage as a normal @acronym{POSIX} filesystem. -@footnote{Some more discussion about this can be found at: - -http://developer.amazonwebservices.com/connect/message.jspa?messageID=52873} - -@menu -* POSIX:: -* BDB:: -@end menu - -@node POSIX -@subsection POSIX -@example -type storage/posix -@end example - -The @command{posix} translator uses a normal @acronym{POSIX} -filesystem as its ``backend'' to actually store files and -directories. This can be any filesystem that supports extended -attributes (@acronym{EXT3}, ReiserFS, @acronym{XFS}, ...). Extended -attributes are used by some translators to store metadata, for -example, by the replicate and stripe translators. See -@ref{Replicate} and @ref{Stripe}, respectively for details. - -@cartouche -@table @code -@item directory <path> -The directory on the local filesystem which is to be used for storage. -@end table -@end cartouche - -@node BDB -@subsection BDB -@example -type storage/bdb -@end example - -The @command{BDB} translator uses a @acronym{Berkeley DB} database as its -``backend'' to actually store files as key-value pair in the database and -directories as regular @acronym{POSIX} directories. Note that @acronym{BDB} -does not provide extended attribute support for regular files. Do not use -@acronym{BDB} as storage translator while using any translator that demands -extended attributes on ``backend''. - -@cartouche -@table @code -@item directory <path> -The directory on the local filesystem which is to be used for storage. -@item mode [cache|persistent] (cache) -When @acronym{BDB} is run in @command{cache} mode, recovery of back-end is not completely -guaranteed. @command{persistent} guarantees that @acronym{BDB} can recover back-end from -@acronym{Berkeley DB} even if GlusterFS crashes. -@item errfile <path> -The path of the file to be used as @command{errfile} for @acronym{Berkeley DB} to report -detailed error messages, if any. Note that all the contents of this file will be written -by @acronym{Berkeley DB}, not GlusterFS. -@item logdir <path> - - -@end table -@end cartouche - -@node Client and Server Translators, Clustering Translators, Storage Translators, Translators -@section 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:: -@end menu - -@node Transport modules -@subsection Transport modules -The client and server translators are capable of using any of the -pluggable transport modules. Currently available transport modules are -@command{tcp}, which uses a @acronym{TCP} connection between client -and server to communicate; @command{ib-sdp}, which uses a -@acronym{TCP} connection over InfiniBand, and @command{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. - -@subsubsection TCP - -The @acronym{TCP} transport module uses a @acronym{TCP/IP} connection between -the server and the client. - -@example - option transport-type tcp -@end example - -The @acronym{TCP} client module accepts the following options: - -@cartouche -@table @code -@item non-blocking-connect [no|off|on|yes] (on) -Whether to make the connection attempt asynchronous. -@item remote-port <n> (24007) -Server port to connect to. -@cindex DNS round robin -@item remote-host <hostname> * -Hostname or @acronym{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. -@end table -@end cartouche - -The @acronym{TCP} server module accepts the following options: - -@cartouche -@table @code -@item 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. -@item listen-port <n> (24007) -The local port to listen on. -@end table -@end cartouche - -@subsubsection IB-SDP -@example - option transport-type ib-sdp -@end example - -kernel implements socket interface for ib hardware. SDP is over ib-verbs. -This module accepts the same options as @command{tcp} - -@subsubsection ibverbs - -@example - option transport-type tcp -@end example - -@cindex infiniband transport - -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 @command{ib-verbs} transport accesses the InfiniBand hardware through -the ``verbs'' @acronym{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 @command{ib-verbs}. Use @command{ib-sdp} only if you cannot get -@command{ib-verbs} working for some reason. - -The @command{ib-verbs} client module accepts the following options: - -@cartouche -@table @code -@item non-blocking-connect [no|off|on|yes] (on) -Whether to make the connection attempt asynchronous. -@item remote-port <n> (24007) -Server port to connect to. -@cindex DNS round robin -@item remote-host <hostname> * -Hostname or @acronym{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. -@end table -@end cartouche - -The @command{ib-verbs} server module accepts the following options: - -@cartouche -@table @code -@item 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. -@item listen-port <n> (24007) -The local port to listen on. -@end table -@end cartouche - -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''. - -@cartouche -@table @code -@item ib-verbs-work-request-send-count <n> (64) -Length of the send queue in datagrams. [Reason to increase/decrease?] - -@item ib-verbs-work-request-recv-count <n> (64) -Length of the receive queue in datagrams. [Reason to increase/decrease?] - -@item ib-verbs-work-request-send-size <size> (128KB) -Size of each datagram that is sent. [Reason to increase/decrease?] - -@item ib-verbs-work-request-recv-size <size> (128KB) -Size of each datagram that is received. [Reason to increase/decrease?] - -@item ib-verbs-port <n> (1) -Port number for ib-verbs. - -@item ib-verbs-mtu [256|512|1024|2048|4096] (2048) -The Maximum Transmission Unit [Reason to increase/decrease?] - -@item ib-verbs-device-name <device-name> (first device in the list) -InfiniBand device to be used. -@end table -@end cartouche - -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. - -@node Client protocol -@subsection Client -@example -type procotol/client -@end example - -The client translator enables the GlusterFS client to access a remote server's -translator tree. - -@cartouche -@table @code - -@item transport-type [tcp,ib-sdp,ib-verbs] (tcp) -The transport type to use. You should use the client versions of all the -transport modules (@command{tcp}, @command{ib-sdp}, -@command{ib-verbs}). -@item remote-subvolume <volume_name> * -The name of the volume on the remote host to attach to. Note that -this is @emph{not} the name of the @command{protocol/server} volume on the -server. It should be any volume under the server. -@item 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. -@end table -@end cartouche - -@node Server protocol -@subsection Server -@example -type protocol/server -@end example - -The server translator exports a translator tree and makes it accessible to -remote GlusterFS clients. - -@cartouche -@table @code -@item 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 @command{--server} option -(@ref{Client}). - -@item transport-type [tcp,ib-verbs,ib-sdp] (tcp) -The transport to use. You should use the server versions of all the transport -modules (@command{tcp}, @command{ib-sdp}, @command{ib-verbs}). - -@item 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 @command{192.168.*.*} -allows any host in the @command{192.168.x.x} subnet to connect to the server. - -@end table -@end cartouche - -@node Clustering Translators -@section 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 @acronym{RAID}-like -redundancy and distribution over the entire cluster. - -There are three clustering translators: @strong{unify}, @strong{replicate}, -and @strong{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:: -@end menu - -@node Unify -@subsection Unify -@cindex unify (translator) -@cindex scheduler (unify) -@example -type cluster/unify -@end example - -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: - -@cindex unify invariants -@itemize -@item The directory structure of all the sub-volumes must be identical. -@item A particular file can exist on only one of the sub-volumes. Phrasing it in another way, a pathname such as @command{/home/calvin/homework.txt}) is unique across the entire cluster. -@end itemize - -@tex -\vfill -@end tex -@page - -@center @image{unify,44pc,,,.pdf} - -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 @emph{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 @emph{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 @emph{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. - -@subsubsection ALU -@cindex alu (scheduler) - -@example - option scheduler alu -@end example - -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: - -@itemize -@item disk-usage: The used and free disk space on the volume. - -@item read-usage: The amount of reading done from this volume. - -@item write-usage: The amount of writing done to this volume. - -@item open-files-usage: The number of files currently open from this volume. - -@item disk-speed-usage: The speed at which the disks are spinning. This is a constant value and therefore not very useful. -@end itemize - -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 -@command{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 necessary. 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 -@command{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: @command{option alu.limits.min-free-disk 5GB}. - -@cartouche -@table @code -@item alu.order <order> * ("disk-usage:write-usage:read-usage:open-files-usage:disk-speed") -@item alu.disk-usage.entry-threshold <size> (1GB) -@item alu.disk-usage.exit-threshold <size> (512MB) -@item alu.write-usage.entry-threshold <%> (25) -@item alu.write-usage.exit-threshold <%> (5) -@item alu.read-usage.entry-threshold <%> (25) -@item alu.read-usage.exit-threshold <%> (5) -@item alu.open-files-usage.entry-threshold <n> (1000) -@item alu.open-files-usage.exit-threshold <n> (100) -@item alu.limits.min-free-disk <%> -@item alu.limits.max-open-files <n> -@end table -@end cartouche - -@subsubsection Round Robin (RR) -@cindex rr (scheduler) - -@example - option scheduler rr -@end example - -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: -@cartouche -@table @code -@item rr.limits.min-free-disk <%> (5) -Minimum free disk space a node must have for RR to schedule a file to it. -@item rr.refresh-interval <t> (10 seconds) -Time between two successive free disk space checks. -@end table -@end cartouche - -@subsubsection Random -@cindex random (scheduler) - -@example - option scheduler random -@end example - -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. - -@cartouche -@table @code -@item random.limits.min-free-disk <%> (5) -Minimum free disk space a node must have for random to schedule a file to it. -@item random.refresh-interval <t> (10 seconds) -Time between two successive free disk space checks. -@end table -@end cartouche - -@subsubsection NUFA -@cindex nufa (scheduler) - -@example - option scheduler nufa -@end example - -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 (@acronym{NUFA}) -scheduler accomplishes that. - -@acronym{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 @acronym{NUFA} schedules files -among the other child volumes in a round-robin fashion. - -@acronym{NUFA} is named after the similar strategy used for memory access, -@acronym{NUMA}@footnote{Non-Uniform Memory Access: -@indicateurl{http://en.wikipedia.org/wiki/Non-Uniform_Memory_Access}}. - -@cartouche -@table @code -@item nufa.limits.min-free-disk <%> (5) -Minimum disk space that must be free (local or remote) for @acronym{NUFA} to schedule a -file to it. -@item nufa.refresh-interval <t> (10 seconds) -Time between two successive free disk space checks. -@item 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. -@end table -@end cartouche - -@cindex namespace -@subsubsection 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. - -@cartouche -@table @code -@item namespace <volume> * -Name of the namespace volume (which should be one of the unify volume's children). -@item self-heal [on|off] (on) -Enable/disable self-heal. Unless you know what you are doing, do not disable self-heal. -@end table -@end cartouche - -@cindex self heal (unify) -@subsubsection 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. - -@node Replicate -@subsection Replicate (formerly AFR) -@cindex Replicate -@example -type cluster/replicate -@end example - -Replicate provides @acronym{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. - -@example -volume replicate-example - type cluster/replicate - subvolumes brick1 brick2 brick3 -end-volume -@end example - -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: -@itemize -@item 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). -@item Allow scheduling of read operations amongst the sub-volumes in a round-robin fashion. -@end itemize - -The order of the subvolumes list should be same across all the 'replicate's as -they will be used for locking purposes. - -@cindex self heal (replicate) -@subsubsection 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: - -@example -volume replicate-example - type cluster/replicate - subvolumes brick1 brick2 -end-volume -@end example - -@subsubsection 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. - -@subsubsection 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 @command{getfattr} command. (@command{getfattr -n trusted.afr.version <file>}) - -@cartouche -@table @code -@item debug [on|off] (off) -@item self-heal [on|off] (on) -@item replicate <pattern> (*:1) -@item lock-node <child_volume> (first child is used by default) -@end table -@end cartouche - -@node Stripe -@subsection Stripe -@cindex stripe (translator) -@example -type cluster/stripe -@end example - -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. - -@center @image{stripe,44pc,,,.pdf} - -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. - -@cartouche -@table @code -@item block-size <pattern>:<size> (*:0 no striping) -Distribute files matching @command{<pattern>} over the sub-volumes, -storing at least @command{<size>} on each sub-volume. For example, - -@example - option block-size *.mpg:1M -@end example - -distributes all files ending in @command{.mpg}, storing at least 1 MB on -each sub-volume. - -Any number of @command{block-size} option lines may be present, specifying -different sizes for different file name patterns. -@end table -@end cartouche - -@node Performance Translators -@section Performance Translators - -@menu -* Read Ahead:: -* Write Behind:: -* IO Threads:: -* IO Cache:: -* Booster:: -@end menu - -@node Read Ahead -@subsection Read Ahead -@cindex read-ahead (translator) -@example -type performance/read-ahead -@end example - -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. - -@cartouche -Options: -@table @code -@item page-size <n> (256KB) -The unit of data that is pre-fetched. -@item page-count <n> (2) -The number of pages that are pre-fetched. -@item 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. -@end table -@end cartouche - -@node Write Behind -@subsection Write Behind -@cindex write-behind (translator) -@example -type performance/write-behind -@end example - -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 -@command{aggregate-size} option is specified, then successive writes up to 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 @command{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. - -@cartouche -@table @code -@item aggregate-size <n> (128KB) -Amount of data to accumulate before doing a write -@item flush-behind [on|yes|off|no] (off|no) - -@end table -@end cartouche - -@node IO Threads -@subsection IO Threads -@cindex io-threads (translator) -@example -type performance/io-threads -@end example - -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. - -@cartouche -@table @code -@item thread-count <n> (1) -Number of threads to use. -@end table -@end cartouche - -@node IO Cache -@subsection IO Cache -@cindex io-cache (translator) -@example -type performance/io-cache -@end example - -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 @command{page-size} chunks. -It caches data up to @command{cache-size} bytes. The cache is maintained as -a prioritized least-recently-used (@acronym{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. - -@cartouche -@table @code -@item page-size <n> (128KB) -Size of a page. -@item cache-size (n) (32MB) -Total amount of data to be cached. -@item force-revalidate-timeout <n> (1) -Timeout to force a cache consistency verification, in seconds. -@item priority <pattern> (*:0) -Filename patterns listed in order of priority. -@end table -@end cartouche - -@node Booster -@subsection Booster -@cindex booster -@example - type performance/booster -@end example - -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 @ref{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 @command{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: - -@example - $ LD_PRELOAD=/usr/local/bin/glusterfs-booster.so your_app -@end example - -The booster translator accepts no options. - -@node Features Translators -@section Features Translators - -@menu -* POSIX Locks:: -* Fixed ID:: -@end menu - -@node POSIX Locks -@subsection POSIX Locks -@cindex record locking -@cindex fcntl -@cindex posix-locks (translator) -@example -type features/posix-locks -@end example - -This translator provides storage independent POSIX record locking -support (@command{fcntl} locking). Typically you'll want to load this on the -server side, just above the @acronym{POSIX} storage translator. Using this -translator you can get both advisory locking and mandatory locking -support. It also handles @command{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. - -@cartouche -@table @code -@item mandatory [on|off] (on) -Turns mandatory locking on. -@end table -@end cartouche - -@node Fixed ID -@subsection Fixed ID -@cindex fixed-id (translator) -@example -type features/fixed-id -@end example - -The fixed ID translator makes all filesystem requests from the client -to appear to be coming from a fixed, specified -@acronym{UID}/@acronym{GID}, regardless of which user actually -initiated the request. - -@cartouche -@table @code -@item fixed-uid <n> [if not set, not used] -The @acronym{UID} to send to the server -@item fixed-gid <n> [if not set, not used] -The @acronym{GID} to send to the server -@end table -@end cartouche - -@node Miscellaneous Translators -@section Miscellaneous Translators - -@menu -* ROT-13:: -* Trace:: -@end menu - -@node ROT-13 -@subsection ROT-13 -@cindex rot-13 (translator) -@example -type encryption/rot-13 -@end example - -@acronym{ROT-13} is a toy translator that can ``encrypt'' and ``decrypt'' file -contents using the @acronym{ROT-13} algorithm. @acronym{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 -@emph{real} encryption (a future release of GlusterFS will have real encryption -translators). - -@cartouche -@table @code -@item encrypt-write [on|off] (on) -Whether to encrypt on write -@item decrypt-read [on|off] (on) -Whether to decrypt on read -@end table -@end cartouche - -@node Trace -@subsection Trace -@cindex trace (translator) -@example -type debug/trace -@end example - -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 @ref{Running GlusterFS}) for trace to work. - -Sample trace output (lines have been wrapped for readability): -@cartouche -@example -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) -@end example -@end cartouche - -@node Usage Scenarios -@chapter Usage Scenarios - -@section Advanced Striping - -This section is based on the Advanced Striping tutorial written by -Anand Avati on the GlusterFS wiki -@footnote{http://gluster.org/docs/index.php/Mixing_Striped_and_Regular_Files}. - -@subsection 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. - -@subsection 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. - -@image{advanced-stripe,44pc,,,.pdf} - -@subsection 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. - -@cartouche -@example - ## 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 -@end example -@end cartouche - -@cartouche -@example - ## 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 -@end example -@end cartouche - - -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: - -@example -[root@@server]# glusterfsd -@end example - -Mounting GlusterFS Volumes: - -@example -[root@@client]# glusterfs -s [BRICK-IP-ADDRESS] /mnt/cluster -@end example - -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. - -@node Troubleshooting -@chapter 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. - -@section GlusterFS error messages - -@subsection Server errors - -@example -glusterfsd: FATAL: could not open specfile: -'/etc/glusterfs/glusterfsd.vol' -@end example - -The GlusterFS server expects the volume specification file to be -at @command{/etc/glusterfs/glusterfsd.vol}. The example -specification file will be installed as -@command{/etc/glusterfs/glusterfsd.vol.sample}. You need to edit -it and rename it, or provide a different specification file using -the @command{--spec-file} command line option (See @ref{Server}). - -@vskip 4ex - -@example -gf_log_init: failed to open logfile "/usr/var/log/glusterfs/glusterfsd.log" - (Permission denied) -@end example - -You don't have permission to create files in the -@command{/usr/var/log/glusterfs} directory. Make sure you are running -GlusterFS as root. Alternatively, specify a different path for the log -file using the @command{--log-file} option (See @ref{Server}). - -@subsection Client errors - -@example -fusermount: failed to access mountpoint /mnt: - Transport endpoint is not connected -@end example - -A previous failed (or hung) mount of GlusterFS is preventing it from being -mounted again in the same location. The fix is to do: - -@example -# umount /mnt -@end example - -and try mounting again. - -@vskip 4ex - -@strong{``Transport endpoint is not connected''.} - -If you get this error when you try a command such as @command{ls} or @command{cat}, -it means the GlusterFS mount did not succeed. Try running GlusterFS in @command{DEBUG} -logging level and study the log messages to discover the cause. - -@vskip 4ex - -@strong{``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: - -@example -telnet IP-ADDRESS 24007 -@end example - -If the server is accessible, your `telnet' command should connect and -block. If not you will see an error message such as @command{telnet: Unable to -connect to remote host: Connection refused}. 24007 is the default -GlusterFS port. If you have changed it, then use the corresponding -port instead. - -@vskip 4ex - -@example -gf_log_init: failed to open logfile "/usr/var/log/glusterfs/glusterfs.log" - (Permission denied) -@end example - -You don't have permission to create files in the -@command{/usr/var/log/glusterfs} directory. Make sure you are running -GlusterFS as root. Alternatively, specify a different path for the log -file using the @command{--log-file} option (See @ref{Client}). - -@section FUSE error messages -@command{modprobe fuse} fails with: ``Unknown symbol in module, or unknown parameter''. -@cindex Redhat Enterprise Linux - -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 @acronym{FUSE} kernel -module, you need to apply the following patch. - -For fuse-2.6.2: - -@indicateurl{http://ftp.gluster.com/pub/gluster/glusterfs/fuse/fuse-2.6.2-rhel-build.patch} - -For fuse-2.6.3: - -@indicateurl{http://ftp.gluster.com/pub/gluster/glusterfs/fuse/fuse-2.6.3-rhel-build.patch} - -@section AppArmour and GlusterFS -@cindex AppArmour -@cindex OpenSuSE -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 @command{glusterfsd} or @command{glusterfs}/@command{fusermount} -should solve the problem. - -@section 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. - -@subsection General instructions - -When running GlusterFS in a non-production environment, be sure to -build it with the following command: - -@example - $ make CFLAGS='-g -O0 -DDEBUG' -@end example - -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. - -@subsection 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. - -@subsection Log files - -Set the loglevel of your client and server programs to @acronym{DEBUG} (by -passing the -L @acronym{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. - -@subsection 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. - -@example - $ gdb ./glusterfs - (gdb) set args -f client.spec -N -l/path/to/log/file -LDEBUG /mnt/point - (gdb) run -@end example - -Now when the process segfaults, you can get the backtrace by typing: - -@example - (gdb) bt -@end example - -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: - -@example - $ gdb /path/to/glusterfs /path/to/core.<pid> -@end example - -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 @command{PID} of -the process (using ps), and then do: - -@example - $ gdb ./glusterfs <pid> -@end example - -Press Ctrl-C to interrupt the process and then generate the backtrace. - -@subsection 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. - -@subsection Other information - -If you think it is relevant, send us also the version of @acronym{FUSE} you're -using, the kernel version, platform. - -@node GNU Free Documentation Licence -@appendix GNU Free Documentation Licence -@include fdl.texi - -@node Index -@unnumbered Index -@printindex cp - -@bye |