If you want to have more than one version of your backup, rsync gained support for that somewhere in the past few years.
You want to look at the "--link-dest" option. Essentially you can keep parallel trees of backups but they use hardlinks to share unchanged files. In practice, backing up web/mail/misc servers I find each extra copy I keep takes about 5% of the first copy's space. rdiff-backup is more space efficient, but 5% isn't much and this is simpler.
If you name the backup trees after the day of the week you don't even have to worry about rotating names and purging old trees, they just overwrite.
(note: you lose the ability to just flop the drive back into the original machine. But I wouldn't do that anyway. I'd use the opportunity for a clean install.)
You want to look at the "--link-dest" option. Essentially you can keep parallel trees of backups but they use hardlinks to share unchanged files. In practice, backing up web/mail/misc servers I find each extra copy I keep takes about 5% of the first copy's space. rdiff-backup is more space efficient, but 5% isn't much and this is simpler.
If you name the backup trees after the day of the week you don't even have to worry about rotating names and purging old trees, they just overwrite.
(note: you lose the ability to just flop the drive back into the original machine. But I wouldn't do that anyway. I'd use the opportunity for a clean install.)