can I tell how much space I would be saving if I switched to ZFS?

Question

I've currently got a spare computer, and I'm thinking of trying out openindiana on it to play around a little with the snapshotting and deduplication features of ZFS, with the view of setting it up for a NAS

I've never actually used a snapshotting or deduplicating file system so... I'm wondering, would df, or its solaris equivalent show how much space I'm actually using with deduplication in place, and would it be simpler (and possible) to have a seperate zfs storage pool to see?

Answer 1

ZFS uses block level dedup rather than file level, so the tool would need to scan every file, create a DB of block hashes and then compare them to detect duplicate blocks. I'm not aware of anything that can do this.

I think the easiest way (if not your only way) would be to test it out. Remember to enable dedup before you start copying the files, the dedup detection only runs on file writes.