Snapshot name collision due to daylight savings
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ddrucker@mclean.harvard.edu November 1, 2020 at 1:48 PM
I guess that does make sense. I should have thought about it more.
Vladimir Vinogradenko November 1, 2020 at 1:24 PM
@ddrucker@mclean.harvard.edu yes, what other suggestions do you have?
ddrucker@mclean.harvard.edu November 1, 2020 at 1:12 PM
Oh, or is the fix simply the allowing of %z?
ddrucker@mclean.harvard.edu November 1, 2020 at 1:10 PM
This bug is still present in 12.0-RELEASE.
Phillip Smith April 21, 2020 at 11:35 PM
Former user No problem - yes it's more of a papercut than anything - the missing snapshot is highly unlikely to actually affect anyone, but it's nice that it's been addressed for 12.0 
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Vladimir Vinogradenko
Vladimir VinogradenkoReporter
Phillip Smith
Phillip SmithFix versions
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Time trackingKatalon Platform
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Katalon Platform
Linked Test Cases, Katalon Defect Results, Katalon Studio Test Results
Created April 6, 2020 at 12:53 AM
Updated July 1, 2022 at 4:49 PM
Resolved April 21, 2020 at 5:41 PM
If FreeNAS is configured to take hourly periodic snapshots, a name collision occurs when daylight savings ends due to the "same" hour occuring twice and the second snapshot failing. This results in a missing snapshot, and an alert:
Snapshot Task For Dataset "yvfm" failed: cannot create snapshot 'yvfm@auto-2020-04-05_02-00': dataset already exists
I suggest either adding the timezone identifier to the snapshot name, or use UTC for the snapshot timestamps (possibly as an optional feature for those in timezones with DST)
Resolution
We need to add something like this to the docs:
If your system is in a timezone that has DST, and you run snapshots every hour or more often, snapshots that should be taken an hour after time goes backwards won't be taken as they already exist. If you want to take such snapshots, you can add "%z" to your naming schema: it will be substituted with strings like "-0300" or ":0700" (":" means "" as ZFS snapshot names can't contain "") to indicate UTC offset of the time at which snapshot was taken.