ispcp needs backup engine overhaul...

[kilburn]

The worst thing about backups is that there's a myriad of ways to handle them, and trying to code something that adapts to everyone's needs is nearly impossible.

For example, I have set up my own backups solution, where:

- My servers are backed up 6 times a day (every 4 hours) to an external backup machine. Copies are time-rolling incremental (using rsnapshot), meaning that, for each server, I have: (1) A copy of its state 4,8,12,16 and 20 hours ago; (2) A copy of its state 1, 2, 3, 4, 5 and 6 days ago; (3) a copy of its state 1, 2, and 3 weeks ago; (4) a copy of its state 1, 2, 3, 4, 5, and 6 moths ago; and (5) a copy of its state 1 year ago. Without storing duplicated data twice, of course.
- The backup server is heavily protected, so it is the one initiating copies (this is, the servers can *not* connect to the backup box for security reasons).
- Backups are made over an lvm snapshot, to avoid the "files being modified" problem.
- Additionally, the backup process runs at a low I/O priority to avoid impacting the server while running. This is, users hardly notice that backups are being made during their execution.

What I'm trying to say with this is that IMHO the best option we have is to provide some *basic* backup functionality, along with some howtos describing alternative backup schemes (such as kurgans' how to transfer an ispcp server using rsync).