> >> We do the same for all of our "legacy" operating system backups. > Take > >> a snapshot then do an rsync and an excellent way of maintaining > >> incremental backups for those. > > > > > > Magic rsync options used: > > > > -a --inplace --no-whole-file --delete-excluded > > > > This causes rsync to overwrite the file blocks in place rather than > > writing to a new temporary file first. As a result, zfs COW produces > > primitive "deduplication" of at least the unchanged blocks (by > writing > > nothing) while writing new COW blocks for the changed blocks. > > If I understand your use case correctly (the application overwrites > some blocks with the same exact contents), ZFS will ignore these "no-
I think he meant to rely on rsync here to do in-place updates of files and only for changed blocks with the above parameters (by using rsync's own delta mechanism). So if you have a file a and only one block changed rsync will overwrite on destination only that single block. > op" writes only on recent Open ZFS (illumos / FreeBSD / Linux) builds > with checksum=sha256 and compression!=off. AFAIK, Solaris ZFS will COW > the blocks even if their content is identical to what's already there, > causing the snapshots to diverge. > > See https://www.illumos.org/issues/3236 for details. > This is interesting. I didn't know about it. Is there an option similar to verify=on in dedup or does it just assume that "checksum is your data"? -- Robert Milkowski http://milek.blogspot.com _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
