EVGA GT1300 doesn't power 4TB Dell SAS drives from its SATA connectors, but does when connected to Molex; Why?

Question

I've been having problems with enrolling some SAS hard drives (on a ZFS ZOL system of mine). I had an EVGA 600w power supply. I thought maybe it was that or cables. I replaced the cables, still had issues. I bought a new EVGA SuperNOVA 1300 GT, 80 Plus Gold 1300W and the problem persists. I have one 2TB SATA system drive, and trying to connect ~4 3TB SAS drives, and ~4 4TB SAS drives, 9 Drives total.

The HBA Card is 01:00.0 Serial Attached SCSI controller: Broadcom / LSI SAS2008 PCI-Express Fusion-MPT SAS-2 [Falcon] (rev 03) but is most likely irrelevant to this situation, since this problem is really about not enough power to the drives from what I can tell.

The 3TB SAS drives have no problems connecting to the SATA power ports on the new PSU. However, I am replacing the 3TB drives with Dell 0F9W8 EMC MG04SCA40EN4TB Drives (Toshiba). For the most part, the 4TB SAS drives will NOT enroll using the SATA connectors on the PSU. They do however work on the Molex connectors. I would obviously like them to work straight from the SATA cables without using any kind of adapters.

I have tested the cables as best as I can, multimeter probing the metal contacts where the wires go into the SATA connector (don't have an official tester, and didn't probe into the actual SATA pins), and they seem well. I also have swapped the 4 triple SATA cables in the modular PSU, amongst the 4 ports. I also swapped the SAS connector from correctly enrolled 3TB drives, to 4TB drives which wont enroll. This test leaves the power connector still connected to the SAS connector, never taking it off, proving that there's an issue powering the 4TB drives.

The conclusion is, the 3TB drives will work fine on all the SATA ports, but the 4TB drives only enroll using the Molex to SATA adapter cable ran off the Molex power cables, but will not run off the default SATA connectors.

There is 12 Sata connectors on this PSU. I think I was able to get one (only) 4tb drive to enroll from one of the SATA ports, but not the rest.

Is there something inherent in these drives where the PSU's SATA cables (with their 3,5,12V terminals) don't need the 3v connections that the SATA ports have in addition that the MOlex don't have?

E>g. its almost as if hooking up a working 3,5,12 cable (PSU's default SATA cable) fails, where a 5,12 (from Molex adapted SATA cable ) doesn't.

This is really confusing.

Could this be bad cables even though swapping the drives shows the cables are working (at least on the 3TB SAS drives)? Or is there a problem with the drives and I just need to stick to adapted Molex->SATA power? Or is this PSU crap, and cant handle the extra load?

Very confused on this one.

It's also disappointing because I got this PSU because it has 12 SATA connectors across 4 busses.

Can someone recommend some testing procedures, or advice on these specific drives if I'm missing something?

Answer 1

The problem was located. There is a power disable feature in modern SAS drives, and maybe even others. There is a WD spec sheet on this here

The issue is the drives are made for a server backplane, which has a function on this pin that keeps it 0 volts. When you issue a drive power-cycle reset it sends a temporary voltage to this pin, which power-cycles the drive. This only happens to drives that have the firmware programmed to do as such.

If your connecting these drives to ATX type PSU's (any maybe other non server and backplane units), these PSU's deliver a constant voltage to this pin, which doesn't allow the drive to spin up at all.

There are several solutions you can use to get the power cut from that 3.3v pin, which will allow it to spin up normally.

See below for a suite of options.

1. For me I was able to use "Kapton Tape" to tape off specific pins on the drive itself. This tape has shown to be able to stay after a couple connections, but is difficult to cut and place this small piece of tape. Its also questionable if you want the tape on your actual drive pins if your drive is not easily hot swappable, since if the tape comes off, you need to remove the drive again to put on a new piece if you frequently are connecting/testing things.

2. Taping the 3rd voltage pin, which is the 3.3v pin, worked fine for me more info on that here. Instead of this option, next time I will probably go with the next option, taping all 3 pins instead.

3. You can tape all 3 of the first voltage pins to play it safe. More info on that here. This link shows taping all 3 pins, which is to play it safe for some cable wiring which links the 3rd pin to the 1st and 2nd. e.g. if you tape the first pin, and your drive still doesnt start, then tape all 3. But its going to be alot easier to cut a piece of tape that size, and should have more stick power as well.

4. You can also physically remove the 1-3rd pins on your SAS adapter cable set, info on that here.

5. One that looks even a bit less maintenance is you get an extension cable, you can cut the first wire on your SATA power connector same link as above here. I would not cut the actual cable from your PSU.

6. You can also simply use the Molex to SATA adapters, which don't supply the 3.3v. The problem with this is, if your getting one of these newer drives, you probably have a newer PSU, and maybe even a bunch of disks (BOD :-)), so the newer PSU's have mostly SATA power connectors, and not Molex. So you don't want to overload your only Molex power line with more than say 3-5 drives, its too much for one line. SO you are probably better off utilizing your many SATA power lines if you have them.

Thanks to @Gantendo for pointing out this issue to begin with.