Help verifying periodic snapshots

[FreeNASBob]

I think he's talking about application level corruption, ie outlook corrupts a .pst or something.

Right. In the past this has happened to me under various circumstances. The worst was when I had used Windows XP's NTFS encryption to encrypt my entire repository of files and then something happened to the NTFS filesystem where NTFS thought they weren't encrypted, but the content of the files was still encrypted. The result was that there was no way to decrypt them at that point, even though I had the password and key. I didn't know when that happened exactly, but if I had snapshots back then I would have noticed when about 50 GB of data had suddenly appeared in a snapshot when it shouldn't have.

Knowing how much data has changed isn't really going to help you determine which snapshot is 'good'.

If I know the size of the corrupted files, it will help immensely.

Poking through the .zfs/snapshots directory is actually a pretty quick way to check various versions of a file in question. And with snapshots exposed through windows' previous version tab, it's even easier.

It can be done, but it's not as convenient.