On Nov 22, 2010, at 17:13, Andrew Reilly wrote:
The currently accepted practice is to create a ZFS file system on the
backup drive and just keep sending incremental snapshots to it. As
long
as the backup drive and host system have a snapshot in common you
can do
incremental transfers. This way you only have to keep the most
recent
snapshot on the main system and can keep as many as you have space
for
on the backup drive. You also have direct access to any backed up
version of every file.
That sounds like a very cool notion. Not unlike the
time-machine scheme. Interesting how different capabilities
require going back and re-thinking the problem, rather than just
trying to implement the old solution with the new tools.
As noted, saving the output of "zfs send" isn't very useful and
generally not recommended as a backup mechanism. It's come up quite
often on Sun/Oracle's zfs-discuss list:
http://www.google.com/search?q=zfs+send/receive+as+backup+tool
In addition to regular snapshots, also make sure to have an offline
backup of some kind (tar, Networker, NetBackup, Amanada, etc.). Errors
can propagate to online copies / backups, and if an intruder can
penetrate your primary system, there's a good chance they can get to
the secondary copy of your data; penetrating a tape on a shelf over
the network would be much more challenging. :)
Newer versions of ZFS also support a "zfs diff" command, but I'm not
sure if that functionality has made it into FreeBSD yet:
http://www.google.com/search?q=zfs+diff
Combine "diff" with some snapshots and scripting, and you can speed up
things like tar and rsync a lot since you don't have to traverse the
entire file system to find changes.
And at the end of the day remember it's not about about backups, but
about restores. If you can't restore coherent data in a timely manner
it's pointless.
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