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I am thinking of purchasing the Dell I580-5108NBC, but I want to add 2 1TB SATA drives in a RAID5 config. The system only has a 300W power supply, and already has a 1TB drive and a DVD burner. Is the 300W power supply sufficient to support two additional drives, or should I upgrade it? Or, can I simply unplug the DVD burner?

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Bear in mind that it may say it's a 300 watt supply, but that's commonly 300 watts Peak, not 300 watts continuous. The PS can probably output about 250 continuously. – Chris S May 27 '10 at 0:52
@Chris I'd say about 210W, going at 70% efficiency (which I believe is still high for a generic power supply) – Sathya May 27 '10 at 17:58
@Sathya: it works the other way around, if it's rated for 300W, that's output, and if it's 70% efficient, it's pulling about 430W from the wall outlet. – Chris S May 29 '10 at 14:51
@Chris: And I measured it, it pulls a peak of 100W from the wall outlet. And the system has been running 24/7 perfectly fine since I asked the question. – Josh Jul 26 '10 at 22:32
up vote 2 down vote accepted

The most effective way to know for sure is to plug them in and see if you start seeing random failures or some components not being recognized. You could also try a PSU Wattage Calculator.

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Is there a less destructive method? :-) – Josh May 27 '10 at 1:53
The wattage calculator. – tsilb May 27 '10 at 6:06
Thanks, the wattage calculator is a great resource, and as @Wayne said, I'm really pushing it... – Josh May 27 '10 at 11:42
I'm going to accept your answer because I ended up doing as you said and just diving right in. The system is running fine with the 300W power supply but I will probably upgrade it soon just to be safe, considering that the calculator said I'd be using ~260W – Josh May 27 '10 at 18:40

A 1TB SATA drive doesn't use that much power. For instance this drive uses 5.4 Watts maximum. Call it 7.5 Watts per drive to be on the safe side and to include the power for the RAID controller. You'll need 15 Watts from the power supply.

Power supplies in packaged systems like the system you suggest are generally sized to match the system. This keeps cost down. However, there's likely enough spare capacity as the 15 Watts is 5% of the total capacity.

You can't unplug the DVD burner without opening the case (I assume you want an internal burner). That's not really practical.

I do wonder though if this PC is right for the a RAID 5 configuration.

  • Does it have enough internal bays to hold the three drives?
  • Does the power supply have enough connectors for the three drives?
  • This seems like a fairly basic system for a RAID 5 configuration. Is an automatic external backup solution better?
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I used tslib's suggested calculator and came up with a figure of 239 Watts for a system similar to yours. So the 300 Watt power supply should do, but it's getting near the limit, especially if as Chris S says the PS can't output the 300 Watts continuously. – Wayne Johnston May 27 '10 at 1:26
The system will be acting as a VMWare Server machine. Once I install the OS I will no longer need the DVD Burner, in fact I may take it out and put it in a different machine. I have to open the case anyway to add the two new drives and it does have the bays required for two more drives. – Josh May 27 '10 at 11:37
@Josh you shouldn't be skimping out on power supply for a regular desktop, let alone a server machine. – Sathya May 27 '10 at 17:59
@Sathya: Thanks. it's on my list of items to purchase! :-) – Josh May 27 '10 at 18:39
@Josh OK :) Just my 2 cents. Seen lot of folks trying to save some cash by skimping out on power supply, only to have their entire system destroyed because of cheap PSUs. – Sathya May 27 '10 at 18:47

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