> Well there's one issue that another whole drive will fail and you're screwed. You do know that in a RAID6 two drives may fail without causing data loss? In a

> Well there's one issue that another whole drive will fail and you're screwed. You do know that in a RAID6 two drives may fail without causing data loss? In any way you need one or more hotspares ready plugged in in order to keep the time window short. RAID6 is not perfect but the probability of 3 drives failing during the rebuilt window is much lower than the probability of 2 drives failing. (One also has to consider errors such as memory corruption, chip failures or catastrophic failure to the power supply where no RAID level will protect you from.) A RAID1 built of two RAID6s may be necessary to avoid performance drops during rebuild. In the case of multiple failures a RAID6+1 setup will protect you from at least 4 hard drives failing in the rebuild time window. > The other issue is that modern disks have an unrecoverable read error rate compared to their size such that a total cover-to-cover read -- necessary on every remaining disk to rebuild a RAID5 -- is kinda unreliable, even with a supposedly healthy disk. This is another reason for a RAID6. Not only does it recover when one or two disks fail. It also recognizes and recovers broken blocks when one disk returns the wrong data. You scrub the disk weekly and remap broken sectors or swap out (soon to break) harddrives.