RE: IBM disk arm reduction "rule of thumb"

["Jones, John \(US\)" <John.Jones@xxxxxxxxxx>]

I think that gain is a combination of several factors:

- Large read/write caches on the 2780 controller
- 15K spindle speed vs. 8K
- Faster ASIC on the RAID card (less time calculating parity)
- Ultra320 SCI drives vs. older 40/80/160MB
- PCI-X bus vs. PCI/SPD
- New machines tend to have more system RAM

It all depends on where your current bottleneck is.  If you've an
SPD-based machine, the SPD bus is more than likely your bottleneck.
It's bandwidth is rather limited.  If you're PCI or better, then the
read/write caches are probably the biggest boost.

But all of the above are contributors.