Well, they are a possible protection against ransomware. In that sense I consider them a backup. But I agree that they do not protect against various other scenarios.
Run, @ChrisRJ. Run. You have spoken such sacrilege.
Iāll try to distract everyone as long as I canā¦ but you need to hurry up and run as far away as possible!
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Yes. As long as snapshots as present all blocks required to serve the multiple versions of the data over time are retained in the pool.
After the second snapshot, blocks 1-3 and 5-10 have two 
, blocks 4 and 11 have one
Used: 11
snaphsot-1: referred 10
snapshot-2: referred 10
Thanks. I think I understand. So if I screw up and delete myfile.dat it can be restored by restoring the snapshot which will contain records of all the blocks and changes. That is the reason to keep your snapshots fresh. Correct?
No idea what you mean by thatā¦
āRestoring a snapshotā, i.e. reverting the whole dataset to the recorded state of a snapshot, is a rather drastic measure as it discards all changes since then.
Rather, you browse the (content of a) snapshot, mounted as a read-only file system, and copy the file back from there into the active datasetāas you do with TimeMachine backups.
ā¦ congratulations, the āHounds of Hadesā TrueNAS forum feature has been unlocked. Good luck outrunning them.
Next up, the Harpies are going to come streaming from the sky, screaming for Vengeance.
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Gotchaā¦I think I finally understand. One more question (maybe) ;-). If you are running snapshots on a regular basic and since snapshots lock and copy blocks how do they keep from using the disk up on a busy dataset that is changing all the time? BTW thanks again for doing this. This has bothered me for a long time and Inquiring minds want to know 
Thatās why snapshots have a limited lifetime. That ability to scroll back in time is limited to whatever you set.
It is common to set multiple snapshot lifetimes - ie hourly snapshots that are kept for 2 weeks, weekly snapshots that are kept for 3 months, for example.
If your data changes a lot, then the space needs for the data will shoot up if snapshots are kept around for a long time. So itās one thing to plan for.
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Ok I think the light is beginning to come on. As snapshots age out it basically unlocks those blocks for reuse and you just lose the capability to go back in time for the data. Snapshots are not a backup so to speak it is a recovery process where you can go back in time to a picture of your data as it was then. The data is only as good as the last snapshot. Right?
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They do more than represent, they refer.
The data referred to by a snapshot, is the actual data that was present when the snapshot was takenā¦ and that data will not be removed from disk until all snapshots that refer to that dataā¦ and the data are deleted.
Now is probably a good time to link my video on Tiered Snapshots, and using them for data recovery 
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Gotcha thanks
Thanks Stuxā¦ I love your videosā¦
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