Running OS X on an external HD

Discussion in 'macOS' started by snverhallen, Oct 26, 2010.

  1. snverhallen macrumors 6502a

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    Oct 17, 2007
    #1
    My internal HD is broken and to repair it I would need to send my iMac and it would take atleast 3 weeks. I don't have another computer and I have really important work to do so I just can't do that.

    Right now I'm using my Western Digital external HD (via USB 2.0) that has my old HD cloned onto it to run OS X on my iMac. I'm thinking about buying a new HD to use as my main HD and use the Western Digital as backup again because I just can't send my iMac away right now.

    So first of all it is OK to run OS X on an external HD right?

    Second, I'm thinking about buying an HD with both USB 2.0 and Firewire 400, namely the LaCie Hard Disk Quadra because it's gotten good reviews on Amazon and I think that using Firewire 400 would be better suited to run OS X with since it can maintain it's data speeds better than USB 2.0.

    Do you have experience with other External HDs I'd love to hear it!

    snverhallen
     
  2. iThinkergoiMac macrumors 68030

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    #2
    Not a problem.

    FW400 is definitely the way to go. If your iMac has FW800, that would be significantly better.
     
  3. lewis82 macrumors 68000

    lewis82

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    #3
    The only problem will be speed, if you don't have enough RAM it could be problematic. If you have enough, opening apps will be slow, but using them will be pretty normal, as they are loaded in RAM.
     
  4. santaliqueur macrumors 6502a

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    Aug 7, 2007
    #4
    I have the 500GB Mercury Elite-AL Pro mini FireWire 800 drive. It's got no external power source, it is powered by the FireWire port. It's silent. I have images of my computers OS X discs on separate partitions for backup/restore. I also have a clean installation of OS X I can boot to at any time. A great device.
     
  5. snverhallen thread starter macrumors 6502a

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    Oct 17, 2007
    #5
    So I have my new LaCie Quadra HD and so far it's been working fine. I just did a read/write test using my USB 2.0 HD and my new LaCie and the USB 2.0 drive got around 18 MB/s and the LaCie around 15 MB/s is this because of the USB 2.0's slightly higher max transfer speed whereas the Firewire 400 is better because it can sustain transfer speeds longer (and therefore better to run OS X on in my case)?

    Thanks,

    snverhallen
     
  6. spinnerlys Guest

    spinnerlys

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    #6
    USB 2.0 should provide faster speeds than 15 or 18 MB/s, my USB HDDs (2.5" or 3.5") give me up to 35 MB/s, though it usually is around 25 to 30 MB/s.

    If your iMac has Firewire 800, why not use the FW800 interface, as FW800 provides speeds of up to 70MB/s?

    And by the following, what exactly did you mean?
    1. You tested another external USB 2.0 HDD, which got 18MB/s via USB 2.0 and you also tested the Quadra via Firewire 400, which only got you 15MB/s?​

    or

    2. You tested another external USB 2.0 HDD, which got 18MB/s via USB 2.0 and you also tested the Quadra via USB 2.0, which only got you 15MB/s?​

    or

    4. You tested another external USB 2.0 HDD, which got 18MB/s via USB 2.0 and you also tested the Quadra via Firewire 800, which only got you 15MB/s?​

    or

    4. something else ...​
     
  7. snverhallen thread starter macrumors 6502a

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    Oct 17, 2007
    #7
    Sorry I should've been clearer, my bad.

    I did the following:

    Copied a 256 megabyte file from the Firewire 400 drive to the USB 2.0 drive.

    Copied a 256 megabyte file from the Firewire 400 drive to the Firewire 400 drive.

    The file was actually made on the fly using the AJA System Test app.
     
  8. spinnerlys Guest

    spinnerlys

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    #8
    How could you copy this AJA System Test file from one drive to the other? As far as I have known AJA ST, it creates the file on the HDD you test and immediately deletes it afterwards. And don't you have Firewire 800?

    [​IMG]


    FW800 port on white iMacs:
    [​IMG]
     
  9. snverhallen thread starter macrumors 6502a

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    #9
    What you said is correct about AJA ST, but you can choose which drive to create the file on.

    And I unfortunately only have 2 Firewire 400 ports.
     
  10. spinnerlys Guest

    spinnerlys

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    #10
    Yes, I know, about the selecting HDD part. I was just confused about you using the phrases:

    and

    as you don't really copy data from one HDD to another, AJA ST just writes one file to the external HDD and reads it again. If the HDD is connected via Firewire, then Firewire is the limiting factor, USB 2.0 has nothing to do with it. Vice versa for an HDD connected via USB 2.0.

    Anyway, the Firewire 400 connection should offer up to 35 MB/s though and the Quadra might be a bit overkill for that, as you paid for the Firewire 800 chipset too. But at least you can use Firewire 800 with any future Mac you might get.
     
  11. snverhallen thread starter macrumors 6502a

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    #11
    I meant to make myself clear with that ^, because I knew those two phrases weren't 100% correct.

    How could I test to see if I get anywhere near the 35MB/s speed?
     
  12. spinnerlys Guest

    spinnerlys

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    #12
    Hmm, AJA System Test should do that though, but maybe you can try Xbench or copy a big file via Finder and monitor the speed via Activity Monitor > Disk Activity?
     
  13. snverhallen thread starter macrumors 6502a

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    Oct 17, 2007
    #13
    OK, thanks for your help!
     

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