ReadyNAS 316 - Disc 5 impending failure warning - leading to question about WD white label drives

While the NAS will complain about it, mixing drive speeds has caused me no issues with my 12-bay rack-mount ReadyNAS's and I have seen no reported issues here that seem to have been caused by a speed mismatch.  The big thing you need to avoid is any SMR drives.  I'm not aware of any 12TB drives that are SMR, but you never know for sure what's in a USB drive until you open it.  Be very careful, too, that you don't end up with one that has the USB circuit built into the drive electronics instead of having a USB to SATA board.  I've heard some now have that.

Personally, I wouldn't go with a shucked drive.  Having had a couple drives fail prematurely that were covered by warranty, I would not risk voiding the warranty for a few dollars (Pounds, Euro, whatever).

What you actually want to get a speed match is the Red Plus (WD120EFBX), not a red.  The 12TB Red was discontinued when they introduced the Red Plus to differentiate the CMR drives from the SMR Reds.  Well, discontinued may be the wrong word, I think they may have simply been re-labeled.