ZFS Snapshots for MDT backup - Revision history

Snehring at 17:52, 23 October 2025

2025-10-23T17:52:50Z

← Older revision		Revision as of 10:52, 23 October 2025
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	That's it. You may notice your MDT consuming more (or less) space depending on the pool geometry of the pool you've sent it to.		That's it. You may notice your MDT consuming more (or less) space depending on the pool geometry of the pool you've sent it to.

			===Incremental backups===
			An extremely powerful feature of zfs snapshots and sends is that you can do incremental sends between two snapshots provided the earlier snapshot also exists on the receiving system.
			<pre>
			# it is assumed that the earlier snapshot (backup-20251022 here) exists on the receiving side
			zfs snap mdt-pool-000/mdt-0000@backup-20251023
			zfs send -vp -i mdt-pool-000/mdt-0000@backup-20251022 mdt-pool-000/mdt-0000@backup-20251023 \| ssh root@backup.server.tld 'zfs recv -s backup-pool/mdt-0000'
			</pre>
			this should send the changes to the dataset from when the first snapshot was taken to the second.

			This can make the migration to new hardware particularly painless as you can do the initial sync while the filesystem is active and then take a shorter downtime to do the final snapshot and send.

	==Restoring your MDT from a backup snapshot==		==Restoring your MDT from a backup snapshot==

Snehring at 16:18, 23 October 2025

2025-10-23T16:18:59Z

← Older revision		Revision as of 09:18, 23 October 2025
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	==Note about backups and restoration==		==Note about backups and restoration==
	Any restoration of a MDT from a snapshot is going to be of the MDT at the point in time the snapshot was created. It is highly likely that unless you also took snapshots of your OSTs at the exact same time as the MDT(s) and restored everything at the same time that the MDT(s) and OSTs will be inconsistent. ~~You~~ will likely have orphaned or missing objects on the OSTs. You should run a lfsck after any restoration.		Any restoration of a MDT from a snapshot is going to be of the MDT at the point in time the snapshot was created. It is highly likely that unless you also took snapshots of your OSTs at the exact same time as the MDT(s) and restored everything at the same time that the MDT(s) and OSTs will be inconsistent. Unless the filesystem was offline when the snapshots were taken you will likely have orphaned or missing objects on the OSTs. You should run a lfsck after any restoration.

	While it may not meet the definition of a backup, just taking snapshots (but not sending them anywhere) on your MDT(s) (and OSTs) can give you a mechanism for rolling back the filesystem should you need to, like due to difficulties during an upgrade for example.		While it may not meet the definition of a backup, just taking snapshots (but not sending them anywhere) on your MDT(s) (and OSTs) can give you a mechanism for rolling back the filesystem should you need to, like due to difficulties during an upgrade for example.

	[[Category:ZFS]]		[[Category:ZFS]]

Snehring: Updating to include the general process for backing up an MDT using zfs snapshots

2025-10-22T20:49:27Z

Updating to include the general process for backing up an MDT using zfs snapshots

@@ Line 1: / Line 1: @@
-In the meantime our old notes are in the comments here: https://jira.whamcloud.com/browse/LUDOC-161
+==Backing up your MDT using zfs snapshots==
-Please add any notes you may have on ZFS snapshots for MDT backup and recovery.
+# Take a snapshot of the MDT dataset
 [[Category:ZFS]]

Snehring: replace jira link

2025-10-15T20:20:30Z

replace jira link

← Older revision		Revision as of 13:20, 15 October 2025
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	At SSEC we are reviewing our MDT snapshot documentation. The basics worked, be had some issues that should be documented.		At SSEC we are reviewing our MDT snapshot documentation. The basics worked, be had some issues that should be documented.

	In the meantime our old notes are in the comments here: https://jira.~~hpdd.intel~~.com/browse/LUDOC-161		In the meantime our old notes are in the comments here: https://jira.whamcloud.com/browse/LUDOC-161

	Please add any notes you may have on ZFS snapshots for MDT backup and recovery.		Please add any notes you may have on ZFS snapshots for MDT backup and recovery.

	[[Category:ZFS]]		[[Category:ZFS]]

Sknolin at 19:08, 6 May 2015

2015-05-06T19:08:05Z

← Older revision		Revision as of 12:08, 6 May 2015
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	At SSEC we are reviewing our MDT snapshot documentation ~~to make sure whatever we put here is accurate for how we do things now~~.		At SSEC we are reviewing our MDT snapshot documentation. The basics worked, be had some issues that should be documented.

	In the meantime our old notes are in the comments here: https://jira.hpdd.intel.com/browse/LUDOC-161		In the meantime our old notes are in the comments here: https://jira.hpdd.intel.com/browse/LUDOC-161

Sknolin: Created page with "At SSEC we are reviewing our MDT snapshot documentation to make sure whatever we put here is accurate for how we do things now. In the meantime our old notes are in the comme..."

2015-05-06T19:06:30Z

Created page with "At SSEC we are reviewing our MDT snapshot documentation to make sure whatever we put here is accurate for how we do things now. In the meantime our old notes are in the comme..."

New page

At SSEC we are reviewing our MDT snapshot documentation to make sure whatever we put here is accurate for how we do things now.

In the meantime our old notes are in the comments here: https://jira.hpdd.intel.com/browse/LUDOC-161

Please add any notes you may have on ZFS snapshots for MDT backup and recovery.

[[Category:ZFS]]