I have 2x500GB hard disk drives in my mac pro currently. The first one is Hitachi, which came with PowerMac G5 Quad while the second one is Seagate, which came with the Mac Pro. I know that the Seagate one is definitely a SATAII HDD while the the older Hitachi one might be a SATAI drive. For this reason, the speed of the 2 drives would be different in theory despite their similar capacity. Question: is it advisable to create a mirror RAID using these 2 hard disk drives? will this RAID work reliably? Also, will the RAID set be slower than if I were to work on the SATAII Seagate hard drive on its own? Thanks for helping.