[wazoox]

> RAID5 is perfectly fine in most instances.

If you're using low capacity, enterprise class SAS drives, mostly, yes. However when using large capacity SATA drives, it most definitely isn't.

SATA drives (even "enterprise" SATA drives) have an official unrecoverable error rate of 1/10^14. From my experience, the truth is more like 1/10^13.

10^13 bits is roughly 10 terabytes. That means that every time you're reading 10 TB, you are statistically certain to encounter an unrecoverable bit error (and have a 1% chance of having 100 errors, of course). In the case of a rebuilding 10 TB array (only a couple 3 or 4 TB drives) using RAID-5, that means that you're almost sure to have an ECC error that will prevent you from ever rebuilding properly without corruption.