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I know this question seems ridiculous, but my server (actually a Mini-ITX computer) has a 2.5" hard drive bay and an empty CD-ROM bay underneath it. If I removed the hard drive bay, I could probably mount a 3.5" hard drive in the CD-ROM bay which is unused...

I know it's a big of a kludgy way to do things but it does mean upgrading the hard drive to 2TB is much cheaper.

My question is: are the power requirements of a 3.5" disk the same as 2.5" one? I know the connectors physically will still fit, but I don't want to destroy my server!

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    2.5 inch drives only need 5 volts to operate, 3.5 inch need 5 volt and 12 volt. the power cable is the same but the requirements are definitely different. That being said it should work just fine.
    – Moab
    Commented Mar 6, 2011 at 15:27
  • What do the bigger drives use the 12v for? Surely they can't take that much more power to spin the platters? I guess the best thing to do is try it out with my existing 320GB 3.5" drive, just to see if it can start up - and then if that works, a drive that's identical (except 2TB - same rotational speed etc i mean) should work too right?
    – Javawag
    Commented Mar 6, 2011 at 15:59

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3.5 inch drives rotating at 5400rpm (all eco green drives etc) compared to 2.5" drives use about twice the power when seeking (as in 6 watts to 3 watts) and four times when idle (4 watts to 1 watt).

The thing to watch out for is the spin-up power use. 3.5" drives can use as much as 2.5 amps on the 12V line (30 watts) for the first second when booting.

It usually is not a problem except when you use low power picoPSU or integrated DC-DC converter - then you should check your 12v line peak rating.

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  • this is interesting actually - i've deliberately got a low power server as it's running in my house and my parents have said if it costs too much to run i'll be paying for the electricity - which is fair enough. do you think those extra few watts will add up over a year or so? i think i'm actually leaning towards getting a 1tb 2.5" drive - 2tb is really a bit excessive anyways, and it'll be cheaper and won't require any hardware changes internally
    – Javawag
    Commented Mar 7, 2011 at 21:44
  • You need to calculate it for yourself - the peak start-up wattage wont affect your bill while the 5 watt idle difference (pessimistic variant) between 2.5 and 3.5 green drive amounts for about $15 per year (for me - I pay, with all taxes, about 18 cents per kWh).
    – Halik
    Commented Mar 10, 2011 at 16:13
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No, the power requirements aren't the same, but the extra power needed shouldn't pose a problem for the power supply. I would find it hard to believe that your PSU wouldn't support a 3.5" HDD when it probably supports an optical drive. Get yourself a 5.25" to 3.5" adapter kit to mount your new HDD, and everything should be fine.

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  • cool :D it does support an optical drive, yeah. It doesn't have one, but the guy who owned the PC before me had one installed but sold it on ebay for some extra money.
    – Javawag
    Commented Mar 6, 2011 at 15:59
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I think the power requirements of a hard drive has more to do with the features than the form factor. So 10,000 RPM drives may pull more juice than 7,200 RPM drives, but a 7,200 RPM drive in either form factor I would think would be the name or nearly the same. On the flip side there are some "green" hard drives out there that take less electricity (although at full use probably still take the same amount as others).

As to where you are mounting the hard drive, I would urge caution. The hard drive is the only moving part in the computer. Hard drives in desktops are not engineered to handle changes in orientation the way the laptop manufacturers include.

So you won't hurt your server, you just need to be careful to securely fit your hard drive. I hear duct tape is fantastic ;-)

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  • Ahh, that's cool. It currently has a 5,400RPM drive but I may upgrade to 7,200... but then again, I'll probably stay with 5,400. Either way, the server won't be moving around at all, but wouldn't hurt to secure the drive in better – the current drive didn't have any fixing screws with it so is held with blu tac ;)
    – Javawag
    Commented Mar 6, 2011 at 2:13

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