Netbackup 6.0

I have Netbackup 6.0 running a backup to disk on an Overland REO 9000. I’m backing up a RaidTEK SAN. When I backup one of my mail servers information stores. I’m getting roughly 25-26 megs per second. When I try backing up my 500 gig File server that has it’s data on the same SAN, I’m getting a rate of 8 mps. I know backing up the information store, since it is 2 files, is going to be a little faster than backing up 500 gig’s of smaller files, but it shouldn’t be this much of a difference. Any thoughts on what I can do to speed this up?