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Can I unplug a hard-drive without Ejecting it first?

Discussion in 'Apple' started by DaveF, Oct 25, 2007.

  1. DaveF

    DaveF Moderator
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    Can I safely unplug an external, USB hard-drive from my Mac without first properly ejecting it? I'm examining whether I want to get an external USB hard drive for my MacBook Pro; but I like to pull the USB hub plug and power cord and take it from my desk. If I also have to first eject a hard-drive, then the nuisance factor starts to creep up too high.

    (I do have an external on my AEBS. But apparently that won't work with Time Machine. [​IMG] )
     
  2. Michael_K_Sr

    Michael_K_Sr Well-Known Member

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    Eject it first. Over time you're going to corrupt data if you just pull the plug. Highlighting the drive and typing COMMAND+E only takes a second or two.
     
  3. DaveF

    DaveF Moderator
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    Thanks Michael. I'll just not plug a USB drive into my MBP. I already forget to unplug my iPod at times, when I "undock". I don't need to put a backup drive at risk.
     
  4. JeremyErwin

    JeremyErwin Well-Known Member

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    There's a little eject icon in the finder that provides an alternative to command-e, should you find that more convenient.

    Doubtless, Apple has rearranged the finder for Leopard, though
    [​IMG]
     
  5. DaveF

    DaveF Moderator
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    I've been looking for a simple Time Machine solution, since it no longer supports drives on the Airport Extreme. Plugging in a drive to the USB hub on my MacBook Pro would be inconvenient; every extra click and cable needed to untether from the desk makes it less usable. If I could unplug with impunity, it would be fine. But if the recommendation is to always Eject a drive before disconnecting -- well, that's just a bother.


    I'm now looking at connecting a drive to my wife's desktop and using Time Machine with that drive, over the wireless network.

    Thanks for the tips and comments.
     
  6. Ken Chan

    Ken Chan Well-Known Member

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    Although it's not because it's some kind of cumulative problem. The issue is that the computer may not be done with the drive. Obviously, if some program is busy writing files to the drive, and you pull the plug, you can lose data. There's no physical way around this, how could there be?

    The act of ejecting a USB/FireWire disk is (in part) you requesting the OS to tell you when it is safe to unplug it. It knows if there are pending writes to the disk. It knows if some application still has some files open, and it won't let you eject it.

    Otherwise, it's Russian Roulette. If nothing is pending or open, you should be able to just pull the plug; things are designed to be tolerant in that way. However, the OS will rightly complain. Because you might think you know if it's safe -- "the light wasn't on" -- but you might be wrong. So you'll do it the one time that trashes something.
     
  7. Al.Anderson

    Al.Anderson Well-Known Member

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    Not quite. The issue is what's called a "delayed write". What is going on is that the operating system buffers the physical I/O to optimize throughput - it's not efficient to write every little bit of data to the hard drive, so the data is stored up until the OS thinks it's a good time for a write. The application could have long ago completed it's write, but the data is in a buffer. Signaling an eject forces the OS to do that last write.
     

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