can the 1U Xserve SATA drives be replaced with larger aftermarket drives?

Hi there everyone I have a new 1U Xserve – 8 core / 2008 model with 3x80GB drives onboard [u]Apple Hardware RAID card[/u] running Leopard Server OS X10.5.1 Due to the expense of Apple Hardware, ive tried swapping out the three 80Gb SATA drives (product no: ST380815AS) which shipped with it for after market Seagate ES.2 1000Gb SATA drives (product no: ST31000340NS). Does anyone know if it's possible to do this ?? Am trying to setup: Bay 1: 80GB OS Bay 2 and 3 as RAID 1 mirror. The drives are recognised, and i've been fully using RAID utility to do this (should i be using Disk Utility instead?). However - am having issues when using RAID utility. The RAID set and RAID volume can be created, it takes about 6 hours to create, and the volume mounts. However when i do a restart the RAID utility alert comes up, and i get a yellow alert - Viable (Degraded). On a restart in RAID 1 the RAID Volume appears on the desktop, however with the yellow degraded alert. When i JBOD both and do a restart they simply don't appear. Any thoughts, or is it 100% not possible to swap these drives for aftermarket when using the standard Hardware RAID card? thank in advance Samoir