Hi,
I would suppliment this with just saying that your controller card is your performance, the only cards I've seen score well on linux, and people have expressed on this list for SCSI are the LSI card, for SATA, LSI, 3ware (now AMCC) and Areca claim good linux support and seem to work well. Steer full clear of Adaptec, Dell and Compaq controllers, and their linux support is abysmal, and the performance reflects that, particularly in RAID 5.
Dell has used (and rebranded) Adaptec and LSI controllers for their PERC series, and I agree that the Adaptec controllers perform badly. As far as I know the LSI based controllers are quite good (and some come with 256MB battery backed cache, which is nice :-)
Sander.
