Bought a 14TB Exos a while back to shuck and use in my array.  I always pre-clear prior to shucking the drive.  Pre-clear went great.

 

When I put it in the array (running 6.12.14, if it matters), while rebuilding the array, it would make an awful whistle/grinding noise every 5 seconds or so.  But it did rebuild.  It worked for a few days, then fell out of sync for some unknown reason.  I plugged the USB panel back in and tested in Windows using SeaTools.  100% fine, no problems.

 

Re-read the above paragraph 2 more times.  3 attempts to rebuild, it works, then falls out of sync.  I have tried everything.  I don't think I can RMA it, because Seagate would test it and it would come back fine.  Anyone else have problems like this with Seagate?  I'd buy another drive and use this in my personal drive, but I'm afraid it will happen again.

How are you powering it when adding it to the main array?   Your description sounds as if there might be a power related issue.  Are you sure your PSU is up to the task?  Also it might be worth trying powering it via a molex->SATA adapter in case you have the a drive that has the "3.3v issue".

My current load is 153W, according to UnRAID's UPS tool.  Maybe something with that branch of the power supply?  Would that be possible?

 

I'm not sure if I have any Molex ports available.  I'll try to shut down the server tonight and see.

To button up this thread, it was already connected to MOLEX, so I knew that wasn't it.  But itimpi made me wonder if that port was bad.  I found a MOLEX splitter and split another port in the PS, and connected it there.  It rebuilt and is running great!  Thanks for the idea!

Great that you found the issue even if it was not exactly what I suggested.