Good question, and you probably shouldn't take my answer as gospel in case Terrible Things happen to your HD... 8) As far as I know, defragmentation makes just as much sense under RAID as it does on any other disk setup, and PageDefrag is just a way of doing that to normally protected system files. If you can't have a separate partition, you might consider having a separate physical disk just for the pagefile. An old, small one would do as long as it's reliable. They tell me that SCSI drives are best, but either way it should speed up your virtual memory operations.