I'm trying to figure out the best fit for doing incremental backups of project and server data on CentOS 5. Specifically, I'm looking for something that supports easy incremental backups at the filesystem level (something lower-level than a versioning system like CVS or Subversion, but not so heavy-duty as full, separate backups (we're looking at using AMANDA for that)). There are a couple of candidates, but I wanted to see if anybody has experience with these issues first:

ZFS looks like it would be good, but the FUSE implementation has some limits on how snapshots are handled, among other things. ext3cow would be perfect, but as far as I can tell it requires a patched kernel of a very specific version, which sounds pretty annoying to manage on CentOS. The lack of fsck, etc. also kind of scares me. Finally, Wayback looks OK too, but is it still actively developed? These were the best systems out of the ones I found, but they all look like pretty small, academic projects. Not necessarily bad, but it makes me a bit nervous not to use something more fully-developed.

I've read plenty about them, but haven't found much in the way of responses from users. Does anybody have any stories about these tools (or others!), good or bad?

I use rsync, with a nifty hard link trick, to do incremental backups. No need for extra software either:
http://www.mikerubel.org/computers/rsync_snapshots/

Works great.

Dave

Thanks Dave, that looks very promising! I didn't realize rsync had all that functionality built in. This might be exactly what I need. Do you happen to know if the mount --bind option he mentions for 2.4 series kernels has a workaround in modern versions? (ie, mounting read-only in one place and read-write in another). It looks like the direct approach won't work (the man page for mount on my home computer, with 2.6.25, explicitly says the --bind option can't do it), but maybe there is a different solution? It would be nice to avoid an unneeded layer of NFS, though I guess if I end up using a dedicated backup machine in the future I'll want it anyway. Anyway, thanks!

I've got the same warning in my mount man page, so I'm going to assume it's not do-able. I generally do backups as root to a directory that's chmod 700 so normal users can't even see the backups, so I've never really thought about read-only access to the backed up data. NFS seems like a decent way of doing this, though.

Dave

OK! I think I've found a workaround for the ZFS FUSE limitation on snapshots, so I'm still on the fence between that and this rsync method. This has the very big plus of being completely standard and portable, though. Whether or not we end up setting up a dedicated backup box is definitely a factor... If we do, I think I'll almost certainly use the rsync method along with NFS or something similar. So anyway, I think I can finally start getting somewhere on this, so thanks again!