>As the disks get bigger, rebuild time also increases and the >performance of the disks don't increase linearly with their storage. >This means that when you are rebuilding a disk, the chances of one of >your other disks failing becomes significantly large. Most suggest >RAID6 these days as a minimum, mirroring and striping appears to be >the most popular. I looked up RAID6 and see the addition or a parity bit. http://en.wikipedia.org/wiki/Standard_RAID_levels#RAID_6 RAID 10 is also something I looked at. Striped, then Mirrored So: 8 x 1.5tb = 12tb RAID 5 = 12tb - 1.5tb for parity data = 10.5tb space available RAID 10 = 4 x 1.5 = 6tb - 1.5tb for parity data = 4.5tb per stripe then mirror it. but with RAID 10, data is safe after many types of failures.