I have a Qnap ts231 NAS and have a Black 4TB and a Red 4tb in it as two separate drives.
Yesterday got a message Raid 1 was not working. Looked and saw my Red was not detected.. Tested in another computer and it was dead. No vibration, no sound, dead!
Took it back to the store and they swapped it for a new one. He said he had more Black returns in past.
Doing a WD diag test on it now. Quick test is fine and now halfway thru extended.
Drive had about 1.5TB data..gone.. This was my backup.