I will second that- put it on a separate server! 3 main reasons:
1) Stability: If you have a issues with either the hardware (bad tape drives happen) or the software (many BE patches require reboots) you can perform this maintenance without affecting your production systems. Wouldn't it be nice to have ONE system that can be worked on during the day?
2) Performance: BE is not a resource hog, but who wants to have users complaining that the file server is slow because you're running the BE database cleanup routines
3) And most important: Recovery! In an all-in-one system, if your server tanks and you need to start from scratch- where are you going to get your catalog? Sure, you can read in the tapes- but at this point it's already 3am, your head hurts and everyone's yelling at you. Feel like another 4 hours of that? Much better to simply turn to your separate- probably unaffected- backup server, select the files from your intact catalog, and let 'er rip! Go home, get a nap, and hope your tapes are good (which is why I always go disk- but that's another thread).