I have installed 5 drives in 2009 Mac Pro - SSD is in Optibay and there are four HDD in bays. Bay 1 - stock 640GB Hitachi drive Bay 2+3 - 750GB WD 750GB Caviar SE16 drives in striped RAID via Disk Utility Bay 4 WD Caviar Green The RAID is slowest of them all which sucks as I wanted to use it as a scratchdisk for HD video editing. Not sure if Im doing something wrong as this is my first time setting up RAID. I might have been a fool though, I bought those two 750GB drives second hand without checking the specs - seller told me they're 7200RPM SATA II drives. I figured it should be enough to saturate Mac Pro's bus. Can anyone elaborate on that? I downloaded AJA System Test Hitachi drive gets 100MBs write/107 read WD Caviar gets 118/130 RAID drives get only 85/88 Tested on 1GB file. I also tried transferring 3GB file to various disks and the RAID is indeed the slowest of them all. Anyone has any idea? My hunch is that I just chose old drives.