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external USB/Firewire drive

Filed under: General — Thomas @ 22:14


I want to buy a big external hard drive (500 GB or more), but I want it to be USB-powered (or Firewire-powered - if that exists) so I only have to plug one cable to have it work. My small Passport drive does this just fine. The external drives I've seen in the store don't mention at all if they do this, and all of them come with a power supply. (I assume it's completely possible to have either work, and that would be fine by me).

Anyone who's bought these things can tell me which ones are USB-powered ?


  1. It’s easy. If the drive it a standard desktop PC drive (3.5 inches), it’s not USB-powered. If the drive is smaller (2.5 inches and less), it is USB-powered.

    Comment by Christian Hudon — 2008-05-22 @ 22:46

  2. Hi,

    common hard drive require some additional voltage to work (like 12V) and it’s impossible to work with only one usb or firewire cable, either for power and data transfert.

    Some disks permit to work only with a computer connection (not an electric one), but usually using 2 or more usb cables. Theorically, usb gives about 5V, and you’ve to using about 3 usb connections only for gives to hard drive sufficent power.

    You either can get an small hard drive (like laptop’s disks)… this use only 2 usb connection (one for data transfert and one for power). This solution speed slowly the hard drive, but permit to using disks without electric power.

    ps: Sorry for horrible english.


    Comment by mouser — 2008-05-22 @ 22:49

  3. As far as I know only 2.5″ drives are low power enough to not require a power supply. And currently there don’t appear to be any 500GB 2.5″ drives. WD’s Passports go up to 320GB at this time. They’re $133 on Amazon[1].

    It’s funny you mention this because not 5 minutes ago I was mulling pulling out an old brick of a hard drive and wrestling cables across my desk to get at some files that MIGHT be there,

    [1] http://www.amazon.com/Western-Digital-Passport-Essential-Portable/dp/B0012GQZZU/ref=pd_bbs_sr_1?ie=UTF8&s=electronics&qid=1211493395&sr=8-1

    Comment by Christopher Sachs — 2008-05-22 @ 23:02

  4. Hi,

    3.5″ drives need 12V power that the USB bus (5V) cannot provide.

    2.5″ drives like the one in your Passport work on 5V.

    You are out of luck, sorry…

    Comment by Nico — 2008-05-22 @ 23:16

  5. USB spec says it provides 5V @ 100mA. SATA power connector specifies 3.3V, 5V, and 12V each @ 4.5A.

    Not sure what the devices/drives themselves require, but if the connector specs are any indication… you may be SOL.

    Comment by Ryan Graham — 2008-05-22 @ 23:23

  6. after googling a bit i found lacie cases that seem to fit your requirements

    LaCie Rugged Hard Disk

    LaCie Little Big Disk Quadra

    Comment by lord rel — 2008-05-22 @ 23:46

  7. Following on from Nico,

    Even if you through a voltage adaptor in there, those your USB ports don’t provide the current you’d then need.

    Even those small USB harddrives usually require you plug in a second ‘for the power’ USB.

    Comment by Davyd — 2008-05-23 @ 01:44

  8. 2.5 inch laptop drives are usb powered, 3.5 desktop ones require an additional power supply, I believe. So to go without a power supply you may have to pay more for a smaller, slower drive.

    Comment by anon — 2008-05-23 @ 02:17

  9. In addition to the comment above…

    USB ports can supply about .5 Amps of power by spec. Only some 2.5″ hard drives can function with this little power, and I have never seen a 3.5″ hard disk that can.

    The largest hard disk I have seen of the 2.5″ type is about 320GB in capacity, although I have heard 500GB is on the horizon.

    Some external drive enclosure manufacturers use a cable that takes power from two USB ports to power the hard disk, thus they are able to support drives that require up to 1 Amp.

    So, for now you are limited to 320GB.

    Comment by Chris — 2008-05-23 @ 03:01

  10. It’s not even a question of voltage. The USB specification simply does not allow enough power to power a full sized drive.

    It can only pull 100mA at start and a maximum of 500mA while running. And the system doesn’t even need to supply that. This is why you won’t see a USB hub for more then 4 ports. 100mA alloted for the hub, and a 100mA for each device (or a maximum of 400mA for a single device, which kinda defeats the purpose of the hub). If they use more then that then you’ll have to get a powered hub.

    Even a lot of laptop harddrives will pull more then that. I have a nice 80GB from a now-dead Ibook that I stuck in a enclosure. It’ll run fine on a single USB line.. until you really start put a load on it then it’ll crap out randomly.

    So either look for a small drive that has a 2.5 inch laptop drive in it or get used to a power cord.

    Comment by Nate — 2008-05-23 @ 03:13

  11. Pretty sure they exist. My friend had an external USB harddrive, not sure of the capacity. Got it from Taiwan. It had two usb connecters on a single cable from the drive, so maybe you had to plug both in to get enough power???

    Comment by Matthew — 2008-05-23 @ 05:06

  12. On top of that, some 2,5″ drives may need a second USB cable because the power the first usb provides isn’t enough to spin them up. But that’s OK in most cases anyway (bar my old ThinkPad which has only two USB ports).

    Comment by Stavros Giannouris — 2008-05-23 @ 06:06

  13. 500GB 2.5″ drive http://www.ecost.com/Detail/External+Storage/Hitachi/0A53487/41069151.aspx

    Comment by arekm — 2008-05-23 @ 15:01

  14. As was already said, so far only 2.5″ drives can be powered over USB; and the biggest drives there are at 320GB. I was looking for exactly the same thing some days ago (external 500GB USB-powered disk, as accessory for an eeepc) and didn’t find anything… I settled with a Maxtor OneTouch 4 Mini instead (250GB, 2.5″, USB-powered, EUR 90). It comes with a Y-shaped USB cord that has one “Power+Data” connector and one “Power” connector.
    Colleague of mine told me that the second connector is not necessary when using USB2 sockets, but well… this is a bit speculative, but for testing I had copied some avi files to the disk, and in the middle of writing one file the drive made weird noises; I later checked the files and found that one file had some big blocks of NUL bytes in it instead of correct content. A badblocks check didn’t reveal anything, so maybe writing to disk without having both connectors plugged in is a bad idea… I have now resorted to making storing md5 sums of most files on disk, to detect any corruption.

    Comment by oliver — 2008-05-23 @ 16:11

  15. I myself am interested in this subject as I have been planning to buy a external hard disk for some time. Some time back I did some study and found that theoretically Firewire interface is more suitable and efficient than USB for high data transfers i.e. something like external hard disk.

    I am surprised to see almost no mention of Firewire in comments above. But as suggested by ‘lord rel’ you may consider the LaCie hard disks.
    The wikipedia page for firewire says that the power supply provided depends on the interface implementation in your machine.[1] Typically it should be 12 V. Please note that 4 pin connectors have no provision for power. You will either need 6 pin (Firewire 400) or 9 pin (Firewire 800) connector.

    [1] http://en.wikipedia.org/wiki/Firewire#FireWire_400_.28IEEE_1394-1995.29

    Comment by Onkar — 2008-05-23 @ 23:45

  16. http://www.iomega.com/direct/products/detail.jsp?PRODUCT%3C%3Eprd_id=53926547&FOLDER%3C%3Efolder_id=58621831&ASSORTMENT%3C%3East_id=26890319&bmUID=1211791764722 Very happy with this one.
    Usb: you do two usb ports to make it run.
    Firewire: just one firewire cable / port and you’re good to go.

    Comment by Hans F — 2008-05-26 @ 09:52

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