Always back up on a dedicated partition or disk!

My home dir on a certain server was backed up by another company. I set under my home a soft link to another location (several Gb of data). What I didn't know: their backup script was rync-based *with* the option --copy-unsafe-links. Rsync followed the link and backed up tons of stuff clugging the backup hard disk. They used the same hard disk and the same partition also for another function: email server. So that softlink disrupted the email server! At first I though I was to be blamed, but after a second thought, I understood, that it's not 100% true: they should have *never* run the mail server on the same partition where they backed up that stuff!