Hi all,

I had 2/3 of my hard drives in a RAIDZ1 ZFS setup fail with the same failure mode. I can't tell you if they failed at the same time, or if one failed in the past and I just never noticed (to be honest, I haven't done any zpool checks or maintenance since I set this array up 6 years ago)...

Before going to a proper HDD specialist, I decided that since it is a redundant setup, I could use one of the HDDs as a guinea pig to see if I could fix it and keep the other one untouched in case I do need to go down the professional route.

So far, no luck and I am scratching my head on what the issue actually is.

HDD
2x
Seagate 4TB NAS
ST4000VN000
PCB version 100710248 Rev C

Symptoms
- HDD not recognized in BIOS. I've tried two different PCs with SATA cables and ports that have been confirmed to work with other HDDs.
- HDD spins up
- There are no clicking of death or beeps, there is a brief noise that occurs twice at t=9 sec in this https://www.youtube.com/watch?v=4UxLMqgqbMU&feature=youtu.be, but then goes away
- There is nothing burnt on the PCB
- Diodes aren't shorted - Mohm+ resistance measured across them with a multi-meter
- Does not appear to be a stuck head

What I have tried so far
- Tried cleaning the contacts on the PCB using an eraser (they were a bit dull)
- PCB swap with two different replacement PCBs I got from HDDZone.com. Neither of them fix the issue. One of them gives the same symptoms, the other one doesn't spin up at all. (and I did do the BIOS IC swap).
- Tried opening the HDD to see if there was a stuck head. Both the platter and the heads seem fine. No signs of scratching. Both platters and head moved easily and don't appear jammed.

Any ideas on anything else to try? Or is this the point I give up and go to a professional?