How Many HDDs on a Cable?

[Lady Fitzgerald]

All PSU SATA power cables I've seen have only four connectors on each cable. Assuming the rail can handle the load and the wire used is large enough to avoid a voltage drop, is there any reason why there can't be more than four HDDs on a cable?

What I am wanting to do is run an SSD (boot/program) and six data drives (probably 2 TB WD Greens) on a single cable that I can make up (the PSU is a modular Corsair HX750; a bit oversized but that will cut down on heat and, hopefully, increase the life of the PSU) to cut down on cable clutter (the case I want to use is a bit tight; space to put it is a problem so it needs to be small). The original cables are made with 18 AWG wire. By using #14 AWG wire, the calculated voltage drop at the last HDD in the string (the SDD would be first) will actually be less than on the Corsair cable. The computer would read or write to no more than two of the HDDs (and the SDD) at any one time. There will also be two hot swap bays (3.5" and 2.5") in the computer (for making back ups) as well as an optical drive but each one of those three will get their own cable.

 

[Mintos45]

so that's 12TB all together on a single cable?

 

[TanyaC]

Technically the WD20EAR[S|X] drives use 1.75A peak (At spin up). The HX750 has a single 12VDC rail that supports up to 62A draw.

So in theory you should have no problems.

At what sustained current draw is 14AWG rated to?

You realise of course though that you are creating a single point of failure? If the cable fails you lose all 7 drives until you replace the cable?

 

[Layback Bear]

What case are you using? Do you have the option to select another case to fit your needs? Their for allowing more cables run properly.

 

[bobafetthotmail]

(the case I want to use is a bit tight; space to put it is a problem so it needs to be small).

Be warned that this setup is better described as "electric heater with 12TB of storage". Keep an eye on their temp and I'm betting that (especially in tight spaces) they will need a dedicated fan or two.

 

[Layback Bear]

Better case, better cooling and use more cables would be my suggestion.

 

[Cr00zng]

At what sustained current draw is 14AWG rated to?

That would be 15A, or about eight HDDs.

The AWG rating is reversed in some sense, the lower AWG rating has higher current rating. The 16AWG is good for 10A, 12AWG 20A, 10AWG 30A, and so on...

 

[Lady Fitzgerald]

so that's 12TB all together on a single cable?

Eventually. I'll start with a couple at first and gradually add HHDs as I need them (I may never reach all six).

Technically the WD20EAR[S|X] drives use 1.75A peak (At spin up). The HX750 has a single 12VDC rail that supports up to 62A draw.

So in theory you should have no problems.

At what sustained current draw is 14AWG rated to?

You realise of course though that you are creating a single point of failure? If the cable fails you lose all 7 drives until you replace the cable?

For 120/240v, it's 15A; 12v is a bit higher (I'm too lazy to look it up again).

Anything can fail. I've never had an internal cable fail nor have I read of one doing so unless something else failed and took the cable with it. If just a single cable to the SSD failed, I would be without a computer anyway. I have my notebook as a backup until I could build another cable.

What case are you using? Do you have the option to select another case to fit your needs? Their for allowing more cables run properly.

The case is an Antec Two Hundred. One reason I wanted this case is because the front panel has a large, easily cleaned filter for the air coming into the case. I live in a very dusty place (Phoenix, AZ area) and some of the haboobs we have been getting lately are the envy of the Middle East. The last one, two days ago, was a wall of dust 2500 ft high and fifty miles long. I could smell the dust inside my closed up home. Even normal dust levels are high so minimizing the dust getting into the case is a huge concern. With this case, I can easily vaccuum the worst of the dust off the filters when they show signs they need it (I'll be able to see it), probably every three or four days (will take all of five minutes or so). Getting at the front filter to do a more thorough cleaning will be easier than most cases I've looked at (the case side panel has to be removed but the innards would need cleaning anyway). Sealing from dust invasion is easier with this case. Although I doubt I'll ever achieve positive case air preassure, I can come close enough to minimize dust intrusion to an acceptable level.

The case already has a 2.5" external HDD swap bay; adding a 3.5" is easy (Antec makes one that fits in a 5.25" slot). That still leaves room for an internal card reader and an optical drive (I still buy a lot of music that does not have downloadable MP3s available so buying CDs is the only option) and rip them to MP3s. I also have a large DVD collection that I will eventually rip (hence the need for a HHD warehouse).

Size is also important. I don't have a whole lot of room for a case where I live now. I plan on eventually moving into a travel trailer (caravan for those on the other side of the pond from me). Fitting a bigger case would be impossible; a separate server to house the storage drives is out also of the question.

(the case I want to use is a bit tight; space to put it is a problem so it needs to be small).

Be warned that this setup is better described as "electric heater with 12TB of storage". Keep an eye on their temp and I'm betting that (especially in tight spaces) they will need a dedicated fan or two.

My current desktop has only an 80mm rear case fan and the 80mm PSU fan pulling air through the case. The side panel has a large grill punched into it and the front of the case has only a small crack to allow air in, and it's well below the HDD, so the HDD (WD 2 TB Green) gets little or no airflow. Still, heating hasn't been a problem.

The Antec has a place for two 120mm fans that get air through the front panel filter and blow it over the HHDs. I will also have a 120mm side panel fan (filtered, of course) and a 120mm rear case fan (there is a 140mm blow hole fan but I'm going to block that off). All the fans will be Thermaltake ISGC 12 (p/n: AF0018), variable speed 800-1300. These fans are reasonably quiet and still move a fair amount of air. Each fan has it's own speed control pot that is easily installed adjacent to the fan (I won't have room for a separate single point fan controller). The 140mm fan in the PSU will pull some air through the case as will, to a lesser degree, the video card. Keep in mind, not all of the HDDs will be running full blast at any one time; the WD Greens are supposed to park the heads when not in use. I'm using one in my XP machine and the head parking is not a problem. Also, this will not be a gaming rig. It won't be overclocked and the vid card will be need only to run three desktop monitors and a couple of TVs (the TVs can use the same feed as the third monitor). If heat with the blow hole blocked becomes an issue, I can always unblock it, put a fan back in there, and just deal with the dust.

 

[gazz9496]

i would usually just assume there was a reason for the limitation, not putting a single point under to much stress, there may also be another reason that the voltage drop off may be too high causing one or more drives not to power up at all or get intermittent power.

can't say i've ever seen anyone do it before, usually just use another cable.