Eight hours to defrag? Leave around 30% free space on each drive. Less free space and it'll start to get painfully slow. I've got a 36 and a 70 gig RAID set and after a clean Windows 2003 install on the bootdrive and SQL Server 2000 + a bunch of DB's on the data drive it takes no more than 2 mins to defrag each drive with the Windows 2003 defragger. Shut down any apps like SQL Server first though. Remote desktop without having to install terminal services is really sweet too