Any study about RAID arrays with identical/different drive models? [closed]

Solution 1:

I know 2 papers about hard-drives and/or RAID:

Using Device Diversity to Protect Data against Batch-Correlated Disk Failures
This one is based on a batch failure, but no discussion about the frequency of such problem.

Disk failures in the real world: What does an MTTF of 1,000,000 hours mean to you?
This one is based on a study against 100,000 disks, and there a little coverage about batches.

Solution 2:

I have never seen a study on RAID arrays specifically, but what you're referring to is called Common Mode Failure in the scientific community and there are plenty of studies on that. Google is your friend.

Anecdotally, like you, I've built RAID (5/6) arrays on many systems for many years and of the half-dozen or so systems I built with identical drives, of the ones that had drive failures, those sets all had multiple drive failures within months of each other. I had one array years ago with 8 identical 9G drives and 6 of them failed within a 6 month window after running fine for 3+ years.. This certainly firmed up my opinion of certain drive manufacturers. On the flip side, of the arrays that didn't have failures, they're still working just fine, one going on 10 years with (enterprise) drives that had a 3 year warranty.

But Common Mode Failure here still applies. I try to mix and match manufacturers on same-sized (enterprise) drives to avoid the issue entirely. (I've also switched to ZFS as well to get past the RAID5 write-hole, but that's another topic).