From: Joseph Spenner <joseph85750 at yahoo.com> > A RAID5 with a hot spare isn't really the same as a RAID6. For those not > familiar with this, a RAID5 in degraded mode (after it lost a disk) will suffer > a performance hit, as well as while it rebuilds from a hot spare. A RAID6 after > losing a disk will not suffer. So, depending on your need for performance, > you'll need to decide. > As far as having a spare disk on a RAID6, I'd say it's not necessary. > As long as you have some mechanism in place to inform you if/when a disk fails, > you'll not suffer any performance hit. Also, if you lose a disk, the RAID6 can lose a second disk anytime without problem. The RAID5 cannot until the hot spare has fully replaced the dead disk (which can take a while). And, I believe RAID6 algorithm might be (a little) more demanding/slow than RAID5. Check also RAID50 and 60 if your controller permits it... JD