Snapshots: Difference between revisions

Revision as of 18:52, 25 November 2020

Snapshots are a implementation of copy-on-write that allows for a file system to quickly take a point-in-time copy of the file system and provide access to the data through a .snapshot directory. Snapshots provide a fast, user-accessible way to recover data that has been accidentally deleted or corrupted within a recent time window -- rather than having to retrieve the data from comparatively slow tape backups. They also help to span the time gap between full backups.

We provide Snapshots on our ZFS, FluidFS, and Isilon filers to certain file systems. If you are ever unsure if a particular volume has Snapshots enabled, please contact the Help Desk.

Snapshot Retention Policy

Our core file systems in the department are on a 4 hour snapshot cycle.

Snapshot Name	Retention Length	When is it taken?
Hourly	24-32 hours	Every day 12am, 4am, 8am, 12pm, 4pm
Daily	2 days	Every day 8pm or 12am
Weekly	1 week	Every Saturday 8pm or Sunday 12am

In other words, we retain up to either 6 or 8 hourly snapshots, 2 daily snapshots and 1 weekly snapshot. Hourly snapshots may be superseded by daily snapshots, and daily snapshots may be superseded by the weekly snapshot.

Snapshot Restoring

If you have deleted a file by mistake and you need to get it back, you can use the snapshots directory to recopy the file.

This directory can typically be found in your home directory. It generally will not be visible, even when viewing hidden directories.

It will be either:

.snapshots for the FluidFS filer
.zfs/snapshot for the ZFS filer
.snapshot for the Isilon filer

The inside of one of these will look something like this on a FluidFS filesystem:

sattwood@zaphod:~$ pwd
/nfshomes/sattwood
sattwood@zaphod:~$ cd .snapshots
sattwood@zaphod:~/.snapshots$ ls
daily_2018_06_14__20_00   hourly_2018_06_14__12_00  hourly_2018_06_15__04_00  weekly_2018_06_09__20_00
daily_2018_06_15__20_00   hourly_2018_06_14__16_00  hourly_2018_06_15__08_00  
hourly_2018_06_14__08_00  hourly_2018_06_14__00_00  hourly_2018_06_15__12_00

Or this, on a ZFS filesystem:

sattwood@swirl:~$ pwd
/nmhomes/sattwood
sattwood@swirl:~$ cd .zfs/snapshot
sattwood@swirl:~/.zfs/snapshot$ ls
zfs-auto-snap_daily-2018-06-13-01h00   zfs-auto-snap_hourly-2018-05-28-00h00
zfs-auto-snap_daily-2018-06-14-01h00   zfs-auto-snap_hourly-2018-05-29-00h00
zfs-auto-snap_daily-2018-06-15-01h00   zfs-auto-snap_hourly-2018-06-03-16h00
zfs-auto-snap_hourly-2018-05-24-00h00  zfs-auto-snap_hourly-2018-06-10-08h00
zfs-auto-snap_hourly-2018-05-25-00h00  zfs-auto-snap_hourly-2018-06-15-12h00
zfs-auto-snap_hourly-2018-05-26-00h00  zfs-auto-snap_weekly-2018-06-09-03h00

Or this, on an Isilon filesystem:

sattwood@coffee:~$ pwd
/nfshomes/sattwood
sattwood@coffee:~$ cd .snapshot
sattwood@coffee:~/.snapshot$ ls
nfshomes_2018-06-14_00:00  nfshomes_2018-06-15_04:00
nfshomes_2018-06-14_16:00  nfshomes_2018-06-15_08:00
nfshomes_2018-06-14_20:00  nfshomes_2018-06-15_12:00
nfshomes_2018-06-15_00:00  Weekly_nfshomes_2018-06-10_00:00

For an example of file restoration, please see this page.

@@ Line 1: / Line 1: @@
-Snapshots are a implementation of copy on write that allows for a file system to quickly take a point in time copy of the file system and provide access to the data through a .snapshot directory.
+Snapshots are a implementation of [http://en.wikipedia.org/wiki/Copy-on-write copy-on-write] that allows for a file system to quickly take a point-in-time copy of the file system and provide access to the data through a .snapshot directory. Snapshots provide a fast, user-accessible way to recover data that has been accidentally deleted or corrupted within a recent time window -- rather than having to retrieve the data from comparatively slow tape backups. They also help to span the time gap between full backups.
-We provide [[Snapshots]] on our [[ONStor]], [[SnapshotsNexenta | Nexenta]] and [[Snapshots:FluidFS | FluidFS]] filers to certain file systems.
+We provide [[Snapshots]] on our ZFS, [[Snapshots:FluidFS | FluidFS]], and Isilon filers to certain file systems. If you are ever unsure if a particular volume has Snapshots enabled, please contact the [[HelpDesk | Help Desk]].
-Please see [[SnapshotFileSystems]] for a list of our file systems that have snapshots in the department.
+==Snapshot Retention Policy==
+Our core file systems in the department are on a 4 hour snapshot cycle.
-==Snapshot Policy==
+{| class="wikitable"
+!Snapshot Name
+!Retention Length
+!When is it taken?
+|-
+|'''Hourly'''
+|24-32 hours
+|Every day 12am, 4am, 8am, 12pm, 4pm
+|-
+|'''Daily'''
+|2 days
+|Every day 8pm or 12am
+|-
+|'''Weekly'''
+|1 week
+|Every Saturday 8pm or Sunday 12am
+|}
-Our core file systems in the department are on a 4 hour snapshot cycle.  Snapshots are taken at,
+In other words, we retain up to either 6 or 8 hourly snapshots, 2 daily snapshots and 1 weekly snapshot. Hourly snapshots may be superseded by daily snapshots, and daily snapshots may be superseded by the weekly snapshot.
-{| style="color:green; background-color:#ffffcc;" cellpadding="5" cellspacing="0"
+==Snapshot Restoring==
-|  12am
-| 4am
-| 8am
-| 12pm
-| 4pm
-| 8pm
-|}
-We retain up to 8 hourly snapshots, 2 daily snapshots and 1 weekly snapshot.
-The [[OpenLAB]] filesystems on which snapshots are available are listed on the [[SnapshotFileSystems]] page.
+If you have deleted a file by mistake and you need to get it back, you can use the snapshots directory to recopy the file.
-==Snapshot Restoring==
+This directory can typically be found in your home directory. It generally will not be visible, even when viewing hidden directories.
-If you have deleted a file by mistake and you need to get it back, you can use the snapshots directory to recopy the file.  This directory can typically be found in your home directory; it will be prepended by a ., so you will need to use the command "ls -a" to find it.  It will be one of three:
+'''It will be either''':
-* .snapshot for the [[ONStor]] (will be removed soon!) / [[Snapshots:NetApp | NetApp]] filers
 * .snapshots for the [[Snapshots:FluidFS | FluidFS]] filer
-* .zfs/snapshots for the [[SnapshotsNexenta | Nexenta]] / [[Snapshots:ZFS | ZFS]] filers
+* .zfs/snapshot for the ZFS filer
+* .snapshot for the Isilon filer
+The inside of one of these will look something like this on a FluidFS filesystem:
-Changing to my quotes directory.
 <pre>
-[derek@novelty quotes]$ pwd
+sattwood@zaphod:~$ pwd
-/nfshomes/derek/work/quotes
+/nfshomes/sattwood
+sattwood@zaphod:~$ cd .snapshots
+sattwood@zaphod:~/.snapshots$ ls
+daily_2018_06_14__20_00   hourly_2018_06_14__12_00  hourly_2018_06_15__04_00  weekly_2018_06_09__20_00
+daily_2018_06_15__20_00   hourly_2018_06_14__16_00  hourly_2018_06_15__08_00
+hourly_2018_06_14__08_00  hourly_2018_06_14__00_00  hourly_2018_06_15__12_00
 </pre>
-I see that i have a quote called  '''redhat_sole_source_2007.doc'''.
+Or this, on a ZFS filesystem:
 <pre>
-[derek@novelty quotes]$ ls
+sattwood@swirl:~$ pwd
-dlt_pdf_quote2007.pdf  Quote_300086759.html         redhat_solesource.pdf
+/nmhomes/sattwood
-dlt_pdf_quote.pdf      Quote_353511914.html         soleSource2007.pdf
+sattwood@swirl:~$ cd .zfs/snapshot
-dlt_quote.pdf          Quote_367512608.html         soleSource.pdf
+sattwood@swirl:~/.zfs/snapshot$ ls
-dy1014.xls             Quote_367884529.html         UMD_008.xls
+zfs-auto-snap_daily-2018-06-13-01h00   zfs-auto-snap_hourly-2018-05-28-00h00
-Quote_250530976.html   redhat_sole_source_2007.doc
+zfs-auto-snap_daily-2018-06-14-01h00   zfs-auto-snap_hourly-2018-05-29-00h00
+zfs-auto-snap_daily-2018-06-15-01h00   zfs-auto-snap_hourly-2018-06-03-16h00
+zfs-auto-snap_hourly-2018-05-24-00h00  zfs-auto-snap_hourly-2018-06-10-08h00
+zfs-auto-snap_hourly-2018-05-25-00h00  zfs-auto-snap_hourly-2018-06-15-12h00
+zfs-auto-snap_hourly-2018-05-26-00h00  zfs-auto-snap_weekly-2018-06-09-03h00
 </pre>
+Or this, on an Isilon filesystem:
 <pre>
-[derek@novelty quotes]$ ls -la redhat_sole_source_2007.doc
+sattwood@coffee:~$ pwd
--rw-r--r-- 1 derek derek 39936 Jan 23  2007 redhat_sole_source_2007.doc
+/nfshomes/sattwood
+sattwood@coffee:~$ cd .snapshot
+sattwood@coffee:~/.snapshot$ ls
+nfshomes_2018-06-14_00:00  nfshomes_2018-06-15_04:00
+nfshomes_2018-06-14_16:00  nfshomes_2018-06-15_08:00
+nfshomes_2018-06-14_20:00  nfshomes_2018-06-15_12:00
+nfshomes_2018-06-15_00:00  Weekly_nfshomes_2018-06-10_00:00
 </pre>
-I will remove it from the current file system.
+For an example of file restoration, please see [[Snapshots:Example | this page]].
-<pre>
-[derek@novelty quotes]$ rm redhat_sole_source_2007.doc
-</pre>
-As you can see it no longer is there.
-<pre>
-[derek@novelty quotes]$ ls
-dlt_pdf_quote2007.pdf  Quote_250530976.html  Quote_367884529.html   UMD_008.xls
-dlt_pdf_quote.pdf      Quote_300086759.html  redhat_solesource.pdf
-dlt_quote.pdf          Quote_353511914.html  soleSource2007.pdf
-dy1014.xls             Quote_367512608.html  soleSource.pdf
-</pre>
-I am going to go into the last hourly snapshot '''hourly.0'''
-<pre>
-[derek@novelty quotes]$ cd .snapshot/hourly.0
-</pre>
-As you can see the quote is still here.
-<pre>
-[derek@novelty hourly.0]$ ls
-dlt_pdf_quote2007.pdf  Quote_300086759.html         redhat_solesource.pdf
-dlt_pdf_quote.pdf      Quote_353511914.html         soleSource2007.pdf
-dlt_quote.pdf          Quote_367512608.html         soleSource.pdf
-dy1014.xls             Quote_367884529.html         UMD_008.xls
-Quote_250530976.html   redhat_sole_source_2007.doc
-</pre>
-I copy it back to the original directory.
-<pre>
-[derek@novelty hourly.0]$ cp redhat_sole_source_2007.doc /nfshomes/derek/work/quotes/
-</pre>
-Change back to the original directory.
-<pre>
-[derek@novelty hourly.0]$ cd /nfshomes/derek/work/quotes/
-</pre>
-And it is back.
-<pre>
-[derek@novelty quotes]$ ls
-dlt_pdf_quote2007.pdf  Quote_300086759.html         redhat_solesource.pdf
-dlt_pdf_quote.pdf      Quote_353511914.html         soleSource2007.pdf
-dlt_quote.pdf          Quote_367512608.html         soleSource.pdf
-dy1014.xls             Quote_367884529.html         UMD_008.xls
-Quote_250530976.html   redhat_sole_source_2007.doc
-</pre>
 [[Category:Snapshots]]
 __NOTOC__

Snapshots: Difference between revisions

Revision as of 18:52, 25 November 2020

Snapshot Retention Policy

Snapshot Restoring

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