But "RAID is not a backup" is not related to this problem though. "RAID is not a backup" s a reflection of the fact that your RAID array is in one location, and

But "RAID is not a backup" is not related to this problem though. "RAID is not a backup" s a reflection of the fact that your RAID array is in one location, and instantly mirrors all data copied to it. A disaster to your storage array outside of a disk failure, will annihilate all your data (and this used to include "RAID controller dies"). The practical issues of RAID rebuilds also don't quite work that way - the "drives die while rebuilding problem" has two components: (1) is that beyond a certain size, the risk of bit-error while resilvering becomes a certainty due to all the data you're reading - ZFS fixes this problem with it's checksums basically. (2) If all your disks were installed at the same time, then the chance of another disk failure is high because they're likely all in the same part of the mean-time-to-failure distribution. (3) the risk of an error is higher because you're doing a lot more activity then normal, and so the additional stress is increasing the chance of triggering a failure.