Putting 6 or 7 SATA drives on one cable safe?

[Suspicious-Teach8788]

Most modular PSUs only come with a connector that has 3-4 SATA power plugs.

I saw this post here:

http://forums.anandtech.com/showthread.php?p=31912258#post31912258

Images here:

where the guy modded the cable to have 6. I'm doing a similar NAS setup and it would be MUCH cleaner if I could do the same thing.

Question is whether this is ok on my power supply or any power supply for that matter? If it helps, I use a Corsair AX-750 which is based on a Seasonic X-750 PSU. It's fully modular.

 

[gevorg]

Modern hard drives consume about 6-8W of power, depending on RPM and brand. So you're looking at 8*6 = 40W which is nothing for your AX-750 PSU. The same cable can be used to feed GPU which consumes even more. My only concern would be if one of drives fail due to power related issue inside, it might affect other drives. Very unlikely, but can't think of anything else.

 

[ericloewe]

If you want to do it, go ahead. It shouldn't be a problem, as long as you know what you're doing when you're modding the cable.

The problem you could face (with any power supply) would be the cable overheating due to excess current, but I think you should be within the cable's specifications. If anything happens, it will almost certainly be at boot during spin-up. You might want to delay drive spin-up, so that they don't all spin-up at once.

 

[Suspicious-Teach8788]

yeah my concern is spinup. Spinup can eat like 16-20W of power. As long as the cable can handle it, then I should be ok.

While staggered spinup is an option, I'd like to not consider it just *in case*

 

[ericloewe]

Yeah, if you only need ~20W at spinup you should be fine.

 

[imagoon]

While I don't think you would have an issue, if you were really worried about it, take a second module cable, add SATA connectors in such a way that the power enters from the bottom and goes up 3 drives. On the other wire it so power enters from the top and goes down.

 

[Charles Kozierok]

Will it work? Probably.

Would I do that in my system? Probably not.

 

[Rifter]

It will work fine, just make sure you use thick enough wire, 18 or 16 gauge would be fine for a bank of 6-10 drives.

 

[billyb0b]

looks nice and clean..... though I don't think i would do it myself. i would put 4 max personally

 

[Smoblikat]

It should work, though drives use the 3.3 5 and 12v lines, so it might be too much current at once through the cables, look into a staggered spinup.

 

[VirtualLarry]

Desktop HDs don't use the 3.3v line, that I know of. At least, I've always been able to use them (SSDs too, so far!), with those molex-to-SATA adaptors, that simply leave off the 3.3v line.

 

[Smoblikat]

Desktop HDs don't use the 3.3v line, that I know of. At least, I've always been able to use them (SSDs too, so far!), with those molex-to-SATA adaptors, that simply leave off the 3.3v line.

Oh, that makes sense now. Would a caviar green be able to use teh 3.3, but not need it. I assume those drives come with some sort of staggered pinup option.

 

[ericloewe]

Desktop HDs don't use the 3.3v line, that I know of. At least, I've always been able to use them (SSDs too, so far!), with those molex-to-SATA adaptors, that simply leave off the 3.3v line.

The original idea for 3.3V in the SATA power connector was to facilitate spinup, but I doubt anyone actually uses it, judging by the problems people face when using molex-SATA adpaters (zero).

 

[RaiderJ]

That picture looks familiar

That setup has been running 24/7 for almost a year now I think. It's solid, not a single error that ZFS has picked up.

Had that exact same question later down in the thread, here's what I posted:

That should depend on a couple of things. My PSU is single rail, so the full power is available over any given connection. Multiple rail PSU's you'd have to make sure you're not exceeding the specific rail that drives are connected to.

I'd have to do some calculations, which would be to take the max load on the cable at drive spin up, and verify that the voltage drop across the cable isn't outside of specification. Each drive takes 2A at spin-up, so I'm pulling 12A total for a short while, then much less during regular operations.

My PSU is rated at 34A on the 12V rail, not sure on the 5V. I think hard drives primarily use the 12V rail on spin-up? Not quite sure. Either way, I have plenty of current available, and I'll assume that voltage drop due to wire resistance and wire length isn't a major factor.

For how many drives I could run off a single cable, I'd want to see how many amps everything else needs to run. I'll assume it needs 14A max for all other devices (which is very generous), leaving ~20A leftover on the 12V rail. That would make me think that I would want to run no more than 10 drives total, and probably not more than 8 of them on a single cable because of voltage drop.

In practice, I bet that you'd be limited on the number of drives connected to a single cable by routing concerns more than anything. Even if you have 20 drives all next to each other, chances are you'd want multiple cables just to make for a cleaner install.