Best Practice for Storing Incremental Clonezilla Images (raw using dd): ZFS Dedup or Snapshots?

OpenZFS
1

Thanks in advance for any advice!

I have an external ZFS backup pool connected via USB that I use to store Clonezilla images of entire drives (these drives aren’t ZFS, but ext4)

My source drive is 1TB, and my destination pool is 2TB, so storage capacity isn’t an issue. I’d like to optimize for space by doing incremental backups, and initially thought deduplication would be perfect, since I’d be making similar images of the same drive with periodic updates (about once a month). The idea was to keep image files named by their backup date, and rely on deduplication to save space due to the similarity between backups.

I tested this, and it worked quite well.

Now I’m wondering if deduplication is even necessary if I use snapshots. For example, could I take a snapshot before each overwrite, keeping a single image filename and letting ZFS snapshots preserve historical versions automatically? The Clonezilla options I’m using create images that are non-compressed and non-encrypted. I don’t need encryption, and the pool already has compression enabled.

Would using snapshots alone be more efficient, or is there still a benefit to deduplication in this workflow? I’d appreciate any advice! I’ve got lots of memory so that isn’t a concern. Maybe I should use both together?

thanks!

2

It depends on whether clonezilla modifies its backup files in place–in which case, yes, you could tell it just to keep a single copy and let snapshots preserve the old versions for you–or creates entirely new files with each run, in which case snapshots wouldn’t do you any good.

I don’t know how clonezilla works, but I suspect that at least by default, it creates entirely new files, for the same reason that rsync (which I do understand the internal workings of quite well) defaults to creating new files. (The reason is because patching files in place is likely to leave you with an inconsistent and effectively unusable file if a patching process is interrupted or crashes in the midst of a run.)

If that’s the case–that clonezilla creates new files rather than patching in-place–then dedup might work for you where simple snapshots would not.