Cross-Platform Backup Software

[Lennart Sorensen]

On Wed, Oct 03, 2007 at 07:18:50PM -0400, Ian Petersen wrote:
> When I "designed" my backup system, one of the first steps was to get
> some new harddrives.  I have a mirrored pair of 250GB drives for my
> main system, but I added a mirrored pair of 500GB drives to hold my
> backups.  I figured that the backup drives won't get as much use as
> the main drives (since I only ever write backups to them once a day),
> so they're less likely to fail (short of the kind of failure that
> takes out an entire machine).  On my todo list are getting a UPS to
> help with power problems, and automated copying of the backup
> repository to Amazon's S3, both of which are supposed to help with the
> kind of failure that takes out an entire machine.

Get a UPS.  Sometimes you get good deals.  My TV (and mythtv box) run on
a SmartUPS 1500.  Nice deal from dell for $200 with free shipping (which
counts for something on a 60 pound box).

> On the other hand, I think rsnapshot keep full versions of every file
> at every backup point and it saves space by reducing unchanged files
> to single files with multiple hard links.

That is right.  Works very well too.  We use that as an online backup
system on our servers so that if people screw up they can go to a
readonly place and get the rsnapshot versions of the file back.

> I'd use a journalling filesystem if only to handle the unlikely
> situation of a system crash _during_ a backup, so I wouldn't recommend
> ext2.  My attitude towards readability is also that you just need to
> keep around one system that can read the backup, which is probably the
> machine that contains the backup itself.  If that system appears to be
> "going out of style", then make a new system and copy the files over.
> Ideally, you'll have two backups--one on-site and one off-site.  If
> either one gets so hosed that you can't use the backup system itself
> to read its backup, you need to rebuild that backup system anyway,
> right?

ext3 saves an awful lot of time at boot time if the previous shutdown
wasn't clean.  Most of the time ext3 doesn't have to run fsck to get
back to a known state, while ext2 can go off on a 2 or 3 hour fsck run
if you have a large disk.  Sure once in a whiile ext3 recommends running
a full fsck just in case, which takes just as long, but at least it is
only once in a while, and you could actually decide when to do it and
schedule downtime for it.

--
Len Sorensen
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