Western Digital just admitted to Tom's Hardware that they use a notoriously slow technology, shingled magnetic recording (SMR), in the WD Red drives they market for use in high performance storage devices. This is a very bad look for them.
I just replaced my last 6TB Red with a Seagate IronWolf over the weekend (coincidentally; it had nothing to do with this). In my experience, Reds have a nasty habit in their old age of taking performance nosedives without reporting any SMART errors. Suddenly my storage volume would be slow and pegged at 100% utilization without anything out of the ordinary running, but everything would look OK otherwise. My NAS's resource monitor would show that all drives are at like 30% utilization, except for a single Red hovering at the top of the graph. The drive would show no errors or really any problems at all, but would be slow as molasses for no apparent reason.
This has happened to me three times now, and each time the fix is to replace the lame duck Red. My storage volume over the weekend was actually faster during the RAID rebuild than it was with the dying drive.
I don't trust Western Digital's drives right now, which is a pity because they use to have a great reputation and I loved them.