>> Plus, once you are on a raid device,
>> logical and physical closeness on the volume no longer mean very much.
I would have thought:
Raid 0: physical distance = logical distance / spindles
Raid 1: physical distance = logical distance
Raid 1 + 0: physical distance = logical distance / spindles / 2
Raid 5: physical distance = logical distance / (spindles - 1)
Certainly caches and elevator seeks can come into play, but it still seems
worth considering the physical distance.
The only array I know of that would not work basically like the above is
Compaq's really high-end EVA system.
I'm sure there are others, but I have to believe the vast majority of arrays
use a very simple block layout.
Deployment and Integration Specialist
Compaq ASE - Tru64
Compaq Master ASE - SAN Architect
The Norcross Group