Re: [tlug] Backup Software

["Stephen J. Turnbull" <stephen@example.com>]

Nicolas Limare writes:
 > On Thu, Nov 25, 2010 at 05:22:45PM +0900, Edward Middleton wrote:
 > > On 11/25/2010 05:02 PM, Nicolas Limare wrote:
 > > >> Alternatively, do you have any ideas for a good backup tool
 > > >> I can use to backup the contents of various linux machines&  servers
 > > >> through the network?
 > > > 
 > > > When it comes to backups I always prefer to use simple, low-tech
 > > > tools, because when something fails or is missing when you need to
 > > > recover the backup, it becomes a nightmare.
 > > > 
 > > > My own solution:
 > > > * rsync everything from all the machines to a central backup server ...
 > > >
 > > > * on each backup server, make snaopshots with rsnapshot
 > > 
 > > How does rsnapshot handle permission and user name changes in
 > > snapshots?
 > 
 > Hmmm.. Good question. As rsnapshot is basically cp -l and rsync, so
 > after a few quick tests I think that when a file metadata (user,
 > perms, atime, ...) changes, rsync will change the attributes of the
 > files in its target directory. And as they are hardlinks to the
 > archived versions, the permissions will be changed for all the
 > identical snapshotted versions.

I wonder if any backup software is based on git (probably git is not
good enough since it doesn't record much metadata).  The point is that
since the git object store is append-only by design, there's no
synchronization problem like you have with any of the disk-to-disk
backup systems, you just check if the file's name equal the SHA hash
of its contents.  When you've filled up a DVD's worth, you just add
the current GIT_OBJECT_DIR to GIT_ALTERNATIVE_OBJECT_DIRS and start a
new one, priming with the contents corresponding to the most recent
backup of the current live filesystem.  The copy-to-backup-media
operation can just use rsync and will be very efficient.  You don't
have to anything special to get rollback capability.

WDYT?