I'm doing some capacity planning for our next generation system and would like to quantify the I/O against a couple 4 different FileGroups in our primary OLTP database.

A couple of facts worth mentioning:
*Running SQL Server 2000
*The file groups are all on the same RAID array, so I can't just watch the physical disks.
*I'm the dba and have full access to any tools available, I just don't know how to understand what the usage pattern is on the underlying objects.

My primary goal is to spec the storage system for the next generation. I'm thinking there is benefit to creating individual RAID arrays, but I'd like to quantify the benefit.

Any experience/knowledge you have to offer is appreciated.