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authorHumble Devassy Chirammal <hchiramm@redhat.com>2015-07-23 17:54:34 +0530
committerHumble Devassy Chirammal <humble.devassy@gmail.com>2015-08-04 05:42:07 -0700
commited9959b0e2c7f401394fa6359641857180baf1c8 (patch)
tree3674ed24345c166335942d801fc87ef7569b28a5 /doc/admin-guide/en-US/markdown/admin_managing_snapshots.md
parent9e3d87639c38b20304ba2809f3f27440ad712fad (diff)
Removing admin guide from glusterfs doc repo
The admin guide is maintained at https://github.com/gluster/glusterdocs. The admin guide updates should be against above repo and we should only have one copy. This is based on the discussion happened here: https://www.mail-archive.com/gluster-users@gluster.org/msg21168.html Change-Id: If5395e7e8005d3e505d229180ce55d466cb1a1fc BUG: 1206539 Signed-off-by: Humble Devassy Chirammal <hchiramm@redhat.com> Reviewed-on: http://review.gluster.org/11747 Tested-by: Gluster Build System <jenkins@build.gluster.com> Reviewed-by: Prashanth Pai <ppai@redhat.com> Reviewed-by: Raghavendra Talur <rtalur@redhat.com>
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-Managing GlusterFS Volume Snapshots
-==========================
-
-This section describes how to perform common GlusterFS volume snapshot
-management operations
-
-Pre-requisites
-=====================
-
-GlusterFS volume snapshot feature is based on thinly provisioned LVM snapshot.
-To make use of snapshot feature GlusterFS volume should fulfill following
-pre-requisites:
-
-* Each brick should be on an independent thinly provisioned LVM.
-* Brick LVM should not contain any other data other than brick.
-* None of the brick should be on a thick LVM.
-* gluster version should be 3.6 and above.
-
-Details of how to create thin volume can be found at the following link.
-https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Logical_Volume_Manager_Administration/thinly_provisioned_volume_creation.html
-
-
-Few features of snapshot are:
-=============================
-
-**Crash Consistency**
-
-when a snapshot is taken at a particular point-in-time, it is made sure that
-the taken snapshot is crash consistent. when the taken snapshot is restored,
-then the data is identical as it was at the time of taking a snapshot.
-
-
-**Online Snapshot**
-
-When the snapshot is being taken the file system and its associated data
-continue to be available for the clients.
-
-
-**Quorum Based**
-
-The quorum feature ensures that the volume is in good condition while the bricks
-are down. Quorum is not met if any bricks are down in a n-way replication where
-n <= 2. Quorum is met when m bricks are up, where m >= (n/2 + 1) where n is odd,
-and m >= n/2 and first brick is up where n is even. snapshot creation fails
-if quorum is not met.
-
-
-**Barrier**
-
-During snapshot creation some of the fops are blocked to guarantee crash
-consistency. There is a default time-out of 2 minutes, if snapshot creation
-is not complete within that span then fops are unbarried. If unbarrier happens
-before the snapshot creation is complete then the snapshot creation operation
-fails. This to ensure that the snapshot is in a consistent state.
-
-
-
-Snapshot Management
-=====================
-
-
-**Snapshot creation**
-
-Syntax :
-*gluster snapshot create <snapname\> <volname\> \[no-timestamp] \[description <description\>\] \[force\]*
-
-Details :
-Creates a snapshot of a GlusterFS volume. User can provide a snap-name and a
-description to identify the snap. The description cannot be more than 1024
-characters.
-Snapshot will be created by appending timestamp with user provided snap name.
-User can override this behaviour by giving no-timestamp flag.
-
-NOTE : To be able to take a snapshot, volume should be present and it
-should be in started state.
-
------------------------------------------------------------------------------
-
-**Snapshot clone**
-
-Syntax :
-*gluster snapshot clone <clonename\> <snapname\>*
-
-Details :
-Creates a clone of a snapshot. Upon successful completion, a new GlusterFS
-volume will be created from snapshot. The clone will be a space efficient clone,
-i.e, the snapshot and the clone will share the backend disk.
-
-NOTE : To be able to take a clone from snapshot, snapshot should be present
-and it should be in activated state.
-
------------------------------------------------------------------------------
-
-**Restoring snaps**
-
-Syntax :
-*gluster snapshot restore <snapname\>*
-
-Details :
-Restores an already taken snapshot of a GlusterFS volume.
-Snapshot restore is an offline activity therefore if the volume is
-online (in started state) then the restore operation will fail.
-
-Once the snapshot is restored it will not be available in the
-list of snapshots.
-
----------------------------------------------------------------------------
-
-**Deleting snaps**
-
-Syntax :
-*gluster snapshot delete \(all | <snapname\> | volume <volname\>\)*
-
-Details :
-If snapname is specified then mentioned snapshot is deleted.
-If volname is specified then all snapshots belonging to that particular
-volume is deleted. If keyword *all* is used then all snapshots belonging
-to the system is deleted.
-
---------------------------------------------------------------------------
-
-**Listing of available snaps**
-
-Syntax:
-*gluster snapshot list \[volname\]*
-
-Details:
-Lists all snapshots taken.
-If volname is provided, then only the snapshots belonging to
-that particular volume is listed.
-
--------------------------------------------------------------------------
-
-**Information of available snaps**
-
-Syntax:
-*gluster snapshot info \[\(snapname | volume <volname\>\)\]*
-
-Details:
-This command gives information such as snapshot name, snapshot UUID,
-time at which snapshot was created, and it lists down the snap-volume-name,
-number of snapshots already taken and number of snapshots still available
-for that particular volume, and the state of the snapshot.
-
-------------------------------------------------------------------------
-
-**Status of snapshots**
-
-Syntax:
-*gluster snapshot status \[\(snapname | volume <volname\>\)\]*
-
-Details:
-This command gives status of the snapshot.
-The details included are snapshot brick path, volume group(LVM details),
-status of the snapshot bricks, PID of the bricks, data percentage filled for
-that particular volume group to which the snapshots belong to, and total size
-of the logical volume.
-
-If snapname is specified then status of the mentioned snapshot is displayed.
-If volname is specified then status of all snapshots belonging to that volume
-is displayed. If both snapname and volname is not specified then status of all
-the snapshots present in the system are displayed.
-
-------------------------------------------------------------------------
-
-**Configuring the snapshot behavior**
-
-Syntax:
-*snapshot config \[volname\] \(\[snap-max-hard-limit <count\>\] \[snap-max-soft-limit <percent>\]\)
- | \(\[auto-delete <enable|disable\>\]\)
- | \(\[activate-on-create <enable|disable\>\]\)*
-
-Details:
-Displays and sets the snapshot config values.
-
-snapshot config without any keywords displays the snapshot config values of
-all volumes in the system. If volname is provided, then the snapshot config
-values of that volume is displayed.
-
-Snapshot config command along with keywords can be used to change the existing
-config values. If volname is provided then config value of that volume is
-changed, else it will set/change the system limit.
-
-snap-max-soft-limit and auto-delete are global options, that will be
-inherited by all volumes in the system and cannot be set to individual volumes.
-
-The system limit takes precedence over the volume specific limit.
-
-When auto-delete feature is enabled, then upon reaching the soft-limit,
-with every successful snapshot creation, the oldest snapshot will be deleted.
-
-When auto-delete feature is disabled, then upon reaching the soft-limit,
-the user gets a warning with every successful snapshot creation.
-
-Upon reaching the hard-limit, further snapshot creations will not be allowed.
-
-activate-on-create is disabled by default. If you enable activate-on-create,
-then further snapshot will be activated during the time of snapshot creation.
--------------------------------------------------------------------------
-
-**Activating a snapshot**
-
-Syntax:
-*gluster snapshot activate <snapname\>*
-
-Details:
-Activates the mentioned snapshot.
-
-Note : By default the snapshot is activated during snapshot creation.
-
--------------------------------------------------------------------------
-
-**Deactivate a snapshot**
-
-Syntax:
-*gluster snapshot deactivate <snapname\>*
-
-Details:
-Deactivates the mentioned snapshot.
-
--------------------------------------------------------------------------
-
-**Accessing the snapshot**
-
-Snapshots can be activated in 2 ways.
-
-1) Mounting the snapshot:
-
-The snapshot can be accessed via FUSE mount (only fuse). To do that it has to be
-mounted first. A snapshot can be mounted via fuse by below command
-
-*mount -t glusterfs <hostname>:/snaps/<snap-name>/<volume-name> <mount-path>*
-
-i.e. say "host1" is one of the peers. Let "vol" be the volume name and "my-snap"
-be the snapshot name. In this case a snapshot can be mounted via this command
-
-*mount -t glusterfs host1:/snaps/my-snap/vol /mnt/snapshot*
-
-
-2) User serviceability:
-
-Apart from the above method of mounting the snapshot, a list of available
-snapshots and the contents of each snapshot can be viewed from any of the mount
-points accessing the glusterfs volume (either FUSE or NFS or SMB). For having
-user serviceable snapshots, it has to be enabled for a volume first. User
-serviceability can be enabled for a volume using the below command.
-
-*gluster volume set <volname> features.uss enable*
-
-Once enabled, from any of the directory (including root of the filesystem) an
-access point will be created to the snapshot world. The access point is a hidden
-directory cding into which will make the user enter the snapshot world. By
-default the hidden directory is ".snaps". Once user serviceability is enabled,
-one will be able to cd into .snaps from any directory. Doing "ls" on that
-directory shows a list of directories which are nothing but the snapshots
-present for that volume. Say if there are 3 snapshots ("snap1", "snap2",
-"snap3"), then doing ls in .snaps directory will show those 3 names as the
-directory entries. They represent the state of the directory from which .snaps
-was entered, at different points in time.
-
-NOTE: The access to the snapshots are read-only.
-
-Also, the name of the hidden directory (or the access point to the snapshot
-world) can be changed using the below command.
-
-*gluster volume set <volname> snapshot-directory <new-name>*
-
-3) Accessing from windows:
-The glusterfs volumes can be made accessible by windows via samba. (the
-glusterfs plugin for samba helps achieve this, without having to re-export
-a fuse mounted glusterfs volume). The snapshots of a glusterfs volume can
-also be viewed in the windows explorer.
-
-There are 2 ways:
-* Give the path of the entry point directory
-(\\<hostname>\<samba-share>\<directory>\<entry-point path>) in the run command
-window
-* Go to the samba share via windows explorer. Make hidden files and folders
-visible so that in the root of the samba share a folder icon for the entry point
-can be seen.
-
-NOTE: From the explorer, snapshot world can be entered via entry point only from
-the root of the samba share. If snapshots have to be seen from subfolders, then
-the path should be provided in the run command window.
-
-For snapshots to be accessible from windows, below 2 options can be used.
-A) The glusterfs plugin for samba should give the option "snapdir-entry-path"
-while starting. The option is an indication to glusterfs, that samba is loading
-it and the value of the option should be the path that is being used as the
-share for windows.
-Ex: Say, there is a glusterfs volume and a directory called "export" from the
-root of the volume is being used as the samba share, then samba has to load
-glusterfs with this option as well.
-
- ret = glfs_set_xlator_option(fs, "*-snapview-client",
- "snapdir-entry-path", "/export");
-The xlator option "snapdir-entry-path" is not exposed via volume set options,
-cannot be changed from CLI. Its an option that has to be provded at the time of
-mounting glusterfs or when samba loads glusterfs.
-B) The accessibility of snapshots via root of the samba share from windows
-is configurable. By default it is turned off. It is a volume set option which can
-be changed via CLI.
-
-gluster volume set <volname> features.show-snapshot-directory "on/off". By
-default it is off.
-
-Only when both the above options have been provided (i.e snapdir-entry-path
-contains a valid unix path that is exported and show-snapshot-directory option
-is set to true), snapshots can accessed via windows explorer.
-
-If only 1st option (i.e. snapdir-entry-path) is set via samba and 2nd option
-(i.e. show-snapshot-directory) is off, then snapshots can be accessed from
-windows via the run command window, but not via the explorer.
-
-
---------------------------------------------------------------------------------------