Mike said: > 3) ZFS ability to recognize duplicate blocks and store only one copy. > I'm not sure the best way to do this, but my thought was to have ZFS > remember what the checksums of every block are. As new blocks are > written, the checksum of the new block is compared to known checksums. > If there is a match, a full comparison of the block is performed. If > it really is a match, the data is not really stored a second time. In > this case, you are still backing up and restoring 50 TB.
I've done a limited version of this on a disk-to-disk backup system that we use - I use rsync with --link-dest to preserve multiple copies in a space-efficient way, but I found that glitches caused the links to be lost occasionally, so I have a job that I run occasionally that looks for identical files and hard links them to each other. The ability to get this done in ZFS would be pretty neat, and presumably COW would ensure that there was no danger of a change on one copy affecting any others. Even if there were severe restrictions on how it worked - e.g. only files with the same relative paths would be considered, or it was batch-only instead of live and continuous - it would still be pretty powerful. Steve. _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
