[plug] Backups

[Craig Ringer]

Marc Wiriadisastra wrote:

> Anyways do I have to mount the file system as read only backup then 
> unmoutn and remount it as read and write.  As I said this sits on 24/7 
> granted its not used constantly and I'm not worried about but its just a 
> situation where I don't want to lose data and the just in case a 
> murphy's stupid laws is what concerns me.

OK. What, exactly, are you trying to accomplish. There are several 
different things people tend to talk about under the heading 'backups', 
and I'm not entirely clear on what you're after. This would seem to be 
an important thing to estabilish before going into too much detail about 
the various availible tools.

Common "backup" tasks include:

- Regular backups of frequently changing information on a system. Often 
done nightly or sometimes weekly..

- Incremental backups, where only information that changed since the 
last backup is backed up.

- Archival style backups, where often large chunks of data are being 
backed up in preparation to either delete the originals to save space, 
or to cease backing up the originals to free up capacity on regular backups.

- System snapshots, where the goal is to make a clone of the entire OS 
and data with the intent of having something that can be restored in a 
total loss situation (system crack, server theft, fire, etc). A system 
snapshot is sometimes being taken with the intent of immediately 
restoring it to another system so that that other system can be used as 
a cold spare/warm spare.

IMHO all of the above are a good idea. I like to use differential 
backups myself (though I'm currently using daily full backups of 
reguarly changing content), combined with off-site archival of older 
data and regular system snapshots.

Nonetheless, it'd be helpful to know what you're currently trying to 
achieve.

--
Craig Ringer