I had an interesting little romp through raid today. I wanted to benchmark a Raid 5 array with Cheetah 15k drives vs Intel Pro SSD drives.
The Cheetah 15k SAS drives were on a Adaptec 6405 controller and the Intel Pro SSD drivers were on an Adaptec 8405 controller. HD Tune benched them at about the same. Average transfer 300MB/s. Then I remembered as I was setting up the SSD array the Adaptec Firmware came back with the message that "we don't recommend enabling read or write cache with SSD drives" so I disabled. I went back in to the controller and enabled both the read and write cache. Lo and behold the average transfer speed doubled to 626MB/s.
So ... anyone have any idea why Adaptec wouldn't recommend the read or write cache with SSD drives? Wow did it make a difference!