Power Disable "Feature" and PSU cabling

foyleswar · February 21

Hey LTT hardware gurus,

Ran into a strange situation. This past December I built an Unraid server using latest gen hardware. I threw 5 Exos drives in it and was off to the races. (1 x X20 and 4 x X10)

I started running low on space, so I bought another X20 from ServerPartDeals. However, the drive refused to spin up in either the Unraid server or my test bench. I decided to try it in my USB enclosure and it worked fine.

After nearly going crazy trying different things, including swapping cables and replacing one of the known good drives with the new drive, I stumbled upon Power Disable. If Power Disable was the problem, switching the power cabling to a Molex > SATA adapter should fix it and wouldn't you know it? That's exactly what worked.

However, I'm completely baffled by why this was necessary and I am struggling to understand how this should work:

Why did the original X20 (and the 4 X10s) work with the 5-wire SATA power cables and not the new drive?
Why would my new Seasonic Focus GX-750 send power on Pin 3 when the SATA 3.2+ spec uses this pin for PWDIS?
Why is it almost impossible to find information related to this and PSUs / PSU cabling?

I'm sticking with the molex fix for now because I don't have any other options - if anyone has advice on how I should handle this for future drives, please let me know.

At this point, I'm thinking I will have to buy 5-wire SATA seasonic cables and clip the 5th wire. But my brain just can't reconcile the stupidity of this - I get it for legacy systems, but why on earth would I need to modify the power cabling in a brand new server?

WhitetailAni · February 21

Just tape over the 3.3v rail with some tape (I used electrical), hard drives don't need it. I had to do this for my Xserve. My HGST 6TB SAS drives work just fine.

foyleswar · February 21

Quote

Thank you for bringing this to our attention. It appears that this item (ST20000NM007D) with firmware "CM01" has a power disable feature. so covering the pin 1 through pin 3 will make the drive work.

Once again appreciate much for the details, I have reiterated this to our product team.

Sincerely,
Chandrika
Server Part deals

Sounds like the OEM drives have different firmware than the ones you buy as 'new' from NewEgg, etc.