poor man's external jbod

A

aitoribarra

Weaksauce
Joined
Sep 16, 2009
Messages
92
Hi,

I will soon be running out of drive bays; but I have plenty of SATA and SAS ports.

I was thinking of using a 5.25" -> 4x 2.5" hotswap, outside the case, powered by an AC -> molex adapter, and running the data cables directly to the available ports.

Are there any electrical problems that can happen? Specifically I'm worried about ground on the data connection going to a different psu to ground on the power connection.

Alternatively could run a long molex cable from a y splitter inside case, but worried about long cable runs, and potential PSU overload (unlikely with 2.5" drives, I know, but).

Any advice appreciated!

Thanks,

Aitor
 
SATA uses differential signaling electrically, and your grounds are going to be very close anyway, so I wouldn't expect any issues, just keep in mind that SATA is specified only up to 1m of cable. Also, most of these 4x2.5" in 5.25" backplanes I've seen use either 4 standard SATA connectors (you'd want some wire loom to keep them in check) or a custom connector (might not be able to get a long enough cable). Don't see why it wouldn't work though if you keep the cables organized.
 
Thanks Keenan!

The server is a rack case, which means that to stay within 1m, I'd probably have to have the backplane near the rear of the case, which would make it a bit awkward to access. I could use SAS drives instead to get a longer cable run, but that could probably be more peak current than the power supply I'm looking at can deliver - luckily I can do staggered spin up.
 
I used 2 PSU to power a single computer for a long time, 1 for the motherboard / hard drives and 1 for the video card / fans / more hard drives without issues. So I doubt that will cause any problem in your case.
 
Thanks Cyant - that's an interesting option too, for another box... how did you get two PSUs to work? Can you just hook up a couple of wires to the motherboard plug to the power switch jumpers on the motheboard, or is it more complicated than that?
 
You dont connect the second PSu to the motherboard at all.


Check this link. http://www.smpspowersupply.com/connectors-pinouts.html
You connect "PS-ON" to one of the grounds. If you un-connect then the PSU shutdown.


Example: Pin 14 + 15 on 20 pin ATX PSU or 16+17 on 24 pin ATX PSU.
THE COLOR ON THE IMAGES IS ONLY A REFERENCE DONT GO BY WIRE COLOR USE PIN NUMBER

At the beginning I used a paper clip to shprt the pins and used the PSU switch to power on and off.

But later I changed the paper clip for a 12v relay connected to a molex of the main PSU (the one connected to the motherboard). That way when the main PSU turned ON the relay switched the Slave PSU by connecting pin 14/15 together.

Very easy to do. make sure you have at least a small load on both 5v AND 12v output of the slave PSU. It's recomended by manufacturers to have a least a small load on each to avoid problem with the PSU. Since you are connecting a couple of hard drive it shouldnt be a problem.

For that you can use cheap empty pc case, they often come with cheap power supply but for that purpose that would be more than enough. They don't have a CPU / videocard to feed and they should have a lot of bays available. Especially if you use 4x 2.5 inch in 1x 5.25 bay adapters.

Have fun with your build!
 
Last edited:
Cyant said:
THE COLOR ON THE IMAGES IS ONLY A REFERENCE DONT GO BY WIRE COLOR USE PIN NUMBER
Click to expand...
I have yet to come across a power supply where black wasn't used for ground and green wasn't used as the PS_ON. Going by colour is usually far easier and faster.
 
Yeah I know but just in case.

They also put warnings to not place animals in microwaves but you'd have to be a dumbass to not know that... heheh
 
If possible tie the gounds together, the hotswap case hopefully has a metal container, then to the main case.
 
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