We also use Arcserve to run the company backups.
It will not backup open files, and as you said, you would have to stop SQL in order to back them up, which is not the most sensible thing to do. Arcserve does have a separate product, an agent that can backup SQL. I believe that it calls SQL's own backup system and dumpos the backup file (Full/Diff/TLog) to tape.
However we experienced problems with this solution and never managed to get a backup we could successfully restore from.
Our solution (which has worked successfully for the past 2 years) was to ensure that SQL ran it's own backups and then we scheduled Arcserver to backup the backup files (if this made sense).
If you want further information about the SQL Agent, let me know and I'll grab one of our network monkeys and get the info off to you.
---------------------------------------
It is by caffeine alone I set my mind in motion.
It is by the Beans of Java that thoughts acquire speed,
the hands acquire shaking, the shaking becomes a warning.
It is by caffeine alone I set my mind in motion.