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Custom cable advice needed

M

MeHoo

n00b
Joined
Apr 17, 2005
Messages
48
I have 6 HDD backplanes that i need to power off of my 750w power supply. Each backplane takes 2 sata and 3 molex connectors. Obviously my power supply doesn't have that many plugs for each so i was going to make some custom cables.

http://c1.neweggimages.com/NeweggImage/productimage/17-995-001-03.jpg

Thats the backplane. I'd like to make the 2 sata and 3 molex all on on string and plug that into either an empty pci-e slot in my modular power supply, or just chain them off of the molex connectors already there.

The problem is that i don't have alot of knowledge of power supplies and i am not sure if theres a limit to how many things you can chain together. Also, i have no idea how to go from a molex to a sata connector, and would be happy to find something online that shows that. http://sierra-cables.com/SATA/Images/SATA-Power-Cable-1.jpg Thats about the best thing i've found so far, but i've never really made one so a how-to would be better if available.

I figure you guys might know more than i do on this so anyhelp is appreciated.
 
To clarify:

I have a SILVERSTONE ST75F PSU. It claims to have 4 12v rails @ 18amps each if that matters. As i said i don't know a LOT about PSUs.

http://www.silverstonetek.com/products/p_spec.php?pno=st75f&area=usa

I have 6 hdd backplanes, but am only currently using 2.
I have 4 pci-e 6-pins but I am not using any so that might be the easiest way to not clutter up the molex rails.

I guess my main concern here is how many HDDs can you run off of one molex rail, or one pci-e rail? I am not finding that info anywhere i look.
 
13 hard drives off the molex/SATA connectors. I've tested this myself with that very power supply. Anything more than that and it would shut off within a second of the power button being pressed.
 
Blue Fox said:
13 hard drives off the molex/SATA connectors. I've tested this myself with that very power supply. Anything more than that and it would shut off within a second of the power button being pressed.
Click to expand...

What kind of hardware is required to do a staggered spinup? Is the RAID controller all that is responsible for that, or do you need support from the enclosure/backplane too? I've never really messed with that stuff, but this thread got me thinking about it since I'm probably going to be setting up a fileserver in a few months.
 
NKDietrich said:
What kind of hardware is required to do a staggered spinup? Is the RAID controller all that is responsible for that, or do you need support from the enclosure/backplane too? I've never really messed with that stuff, but this thread got me thinking about it since I'm probably going to be setting up a fileserver in a few months.
Click to expand...
Both. I used molex --> SATA adapters that lacked the 3.3v line, so I couldn't do staggered startup even though my RAID card supports it. I switched to a single rail PSU (610w PC P&C to be exact) as the Silverstone I had wasn't cutting it.
 
hmm.. well my Areca 1231ml supports 12 drives so i think i'll be safe at least until i need to get another card. I planned on running pci-express to molex/sata and hoping for the best.

Blue Fox:
Is it worth it to get a better power supply?

I have a week ro so to return this one if so.

Also, what is the benefit of the single rail, and how do you keep the ability to use the staggered spin-up capabilities of the raid card?
 
Well, as I said, you'll need to provide the 3.3v line to allow staggered startup. If you are going to only use 12 drives, then I wouldn't worry about it. I wouldn't get a different power supply since you plan on getting much of the power from the other rails. I was only using one rail, so it wasn't working too well. Only benefit from the single rail PSUs is that you don't have to do any modification like what you are doing.
 
I would imagine the PCI Express to Molex would not work for hard drives, as PCIe connectors only have 12 volt lines. Hard drives need at least 12v and 5v.
 
damn.. good call. ok well i guess i need to order up some more molex connectors =] thanks for the heads up
 
Just out of curiosity.. how does the staggered spin up work? If i draw a 3.3v line off of the two sata connectors by simply doubling the 5v line and adding a resistor, would this be bad?
 
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