Guaranteed snapshot space and restoring question

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occamsrazor
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Guaranteed snapshot space and restoring question

Post by occamsrazor » Thu Aug 22, 2019 4:02 pm

Probably a dumb question but... Am setting up a new set of disks from scratch and want to enable snapshots, with guaranteed snapshot space.
Say I have single storage pool occupying the entire Raid-5 disk space of 30TB, create a single thick volume of 25TB, and set a guaranteed snapshot space of 5TB.
I then fill that thick volume with 23TB of files.
Then later I accidentally delete ALL those 23TB of files.
I know the guaranteed snapshot space represents the maximum size of changes tracked, but assuming I don't create large amounts of new data on the volume then in this case I should still be able to restore ALL those 23TB of files...... is this correct? Or no?
TS-451 [4 x 10TB WD Reds in Raid-5]
TS-239 Pro II [2 x 3TB in Raid-0]
pfSense router and Ubiquiti Unifi switches
Mac Minis, MacBook Pro, iPhones

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storageman
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Joined: Thu Sep 22, 2011 10:57 pm

Re: Guaranteed snapshot space and restoring question

Post by storageman » Fri Aug 23, 2019 12:14 am

Correct, the snapshot before you did the deletion should only contain the pointers to the files so I would say all 23TB should be restorable.
The deleted files are marked for deletion meaning the space can be overwritten by later writes.
Your problem would only be if the total changes over all the snapshots taken exceeded 5TB.

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