Raid 1 can indeed reduce the "apparent" read access time. But the "apparent" write time also increase - but on most HP e3000, the write time isn't a problem. The writes are handled in the background by XM, so you are a little removed from the actual impact. The problem with read requests on Raid-5 is that it actually can't return the data until it has gotten the data off the corresponding data stripes and verified the parity. Which means the drive seek and rotation times become much more noticeable. This can be fixed by using special drives that can have the spindles synchronized so that the sector 0 is under the heads for all the drives at the same time. Most Raid-5 controllers have a pretty good size cache, which means writes can appear to complete very quickly --- while the controller actually writes the stripes. In the PC world, there are several pretty good disk controllers that allow you to choose Raid-1 mirroring or Raid-5 striping. I believe that both the Promise and Adaptec, when operated in a mirrored disk mode will actually return the data from which ever drive responds first -- similar to Mirrored disk/iX. Most of the PC raid adapters also provide utilities so that you can be alerted when a drive fails. A good reference site is www.raid5.com, look for the "raid.edu" tab.