Sorin Srbu wrote:
Today I have five 500GB-disks raided on linux machine. Remove one for parity and I have 2TB of real space available. Doing a 0+1, ie 1TB, would indeed be better as performance goes, but 1TB of space, well, it just isn't enough unfortunately.
As it is now, the 2TB shebang is mounted as /backup. Does that count as a single filesystem?
If you have any budget at all, invest in bigger drives. 7200 RPM 1 TB RAID rated drives can be bought for $160 each. Desktop rated 5900 RPM 1.5 TB drives (which you can probably get away with in a dedicated backup server since you don't care a lot about speed and can tolerate long pauses for sector repair) can be bought for $110 each. Check Newegg.
Second, to maximize 'depth' of backups you should use a 'Tower of Hanoi'-like backup system.
For example:
1 day 2 days 4 days 8 days 16 days
etc
If your selected backup software supports either hardlinking or plain old incremental backups that will keep the size of backups down a lot while giving you history.