My understanding is that raid 5 requires the same size/interace of drives, not same make and model (i.e. all need to be, say, 200gb sata drives, not model xxx maxtor 200gb sata drives). Thus, as long as 200gb sata drives are still available, I should be all set if/when one fails. Regarding simultaneous failure -- this is why I've only bought 2 so far -- I've heard it's best to build an array with, at a minimum, drives that were built on different days/etc. --