I usually use the surveillance-line of disk drives. That's WD Purple, Seagate Skyhawk, or Toshiba S300. Theoretically, their firmware is supposed to be tuned to

I usually use the surveillance-line of disk drives. That's WD Purple, Seagate Skyhawk, or Toshiba S300. Theoretically, their firmware is supposed to be tuned to a higher queue depth and lower latency, which should be beneficial to RAID performance. Haven't run any performance numbers on them, though.