I'm installing BM 3.8 on a Proliant DL380. This server has three 72GB
drives. It's been suggested that the CACHE volumes be on separate
physical disks than the SYS: volume, but I'm not sure how to do that
with just three physical drives. The only safe method I can see would
be to mirror (RAID 1) the SYS: partition and put a single cache volume
on the remaining disk, but I'd really like to have more than one cache

Is it worth the trouble to obtain and install a fourth drive so I can
mirror SYS: and have two physical drives dedicated to caching?