> From: tech-boun...@lists.lopsa.org [mailto:tech-boun...@lists.lopsa.org] > On Behalf Of Skylar Thompson > > I think checksumming has a place in backup/archive systems, but I'm not sure > that end-to-end checksumming will allow sufficient scalability, at least with > current filesystem technology. At $WORK, if we had to checksum each file on > each filesystem we backup, I doubt we could complete our backups in our > window,
Right on. If you have block-level or filesystem-implemented data integrity, then you can rely on the filesystem. But without it, the only way you can check is to run a huge intensive scan. You definitely DON'T want to do that on every send, but you definitely WANT or NEED to do it sometimes. With a checksumming filesystem (at least, with btrfs & zfs) you're not likely to do your backups with tar or rsync or anything else. You're virtually certain to use zfs send, or btrfs send. It has also the benefit of not needing to walk the filesystem searching for changed stuff. But without those filesystems, it's very useful to be able to keep linearly rolling incremental backups, including a command to validate all your data, and perform validation upon restores as well. I do believe btrfs will obsolete ext someday. But I don't believe ext is going extinct any time soon. > What I think /could/ work, though, is if checksumming filesystems like ZFS > could expose the checksum data to user applications (like backup clients), The reason that's not possible is because the ZFS checksums don't relate to the files. They relate to data blocks, which may be file fragments, or contain multiple files, and always include various forms of filesystem metadata. So you'll always have to utilize your ZFS checksums via zfs internal commands. You can scrub your whole pool... There might be a fringe use case where it's useful to just validate the blocks that are related to certain files, without doing the whole pool... But I can't think of such a use case. _______________________________________________ Tech mailing list Tech@lists.lopsa.org https://lists.lopsa.org/cgi-bin/mailman/listinfo/tech This list provided by the League of Professional System Administrators http://lopsa.org/
