If your OS supports it, and VMS and *BSD do,
I've found that remote
filesystems outperform local RD5x storage by a very comfy margin. I
haven't had the pleasure of running SDI disks, so I dunno how they'd
match up.
I do know that my MVIII uses a hack of a lot less power booting off a
remote disk than it did spinning up 3 MFM drives. I can only assume
that the RAxx use even more juice.
By a remote disk, I assume you're talking about a 3.5" SCSI disk sitting in
a remote VMS or *BSD box? In such a configuration you still should (if
possible) have a local swap disk.
Zane