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Time it takes to erase disk

384 Views 18 Replies Latest reply: Feb 22, 2013 12:42 AM by seventy one RSS
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seventy one Level 6 Level 6 (8,525 points)
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Feb 21, 2013 4:35 AM

I am erasing an external disk using the 7 pass option.   The disk was holding 150 GB.   The estimated time jumps every time I look; it started at 16 hours and is now 1 day and 13 hours.   Is there a rule of thumb calculation as to how long it is likely to take.   Oh, and can I put the machine into sleep mode while it is going on?

Mac OS X (10.6.8)
  • Klaus1 Level 8 Level 8 (43,430 points)
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    Feb 21, 2013 9:41 AM (in response to seventy one)

    seventy one wrote:

     

    Bump.   Would anyone have an idea?

    Not until you post back and tell us how long it took!

     

    Sleep the screen but not the hard drive.

  • varjak paw Level 10 Level 10 (167,195 points)
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    Feb 21, 2013 9:52 AM (in response to seventy one)

    According to another site where the poster timed it, the 7-pass erase takes 0.314 minutes per gigabyte per pass. And it will erase the entire drive, not just the amount of data stored. You can do the calculations yourself to get an estimate of how long it will take for your drive, though of course differences in the speed of your system and of the drive may cause your milage to vary.

     

    Regards.

  • Klaus1 Level 8 Level 8 (43,430 points)
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    Feb 21, 2013 9:54 AM (in response to varjak paw)

    Where is the fun in that? I was going to suggest we run a sweepstake!

  • varjak paw Level 10 Level 10 (167,195 points)
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    Feb 21, 2013 2:05 PM (in response to seventy one)

    It's not a formula. It was an actual measurement made by another user. And as I said the size of your drive and its performance will affect the actual time it will take. So if you have a large drive that is rather slow, it could indeed take a couple of days. A fast 500GB drive would take over 18 hours.

  • WZZZ Level 6 Level 6 (11,880 points)
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    Feb 21, 2013 2:19 PM (in response to seventy one)

    Unless you are expecting dedicated analysis using an electron microscope by some agency like the NSA, the 7 pass is totally unnecessary. One pass erase is more than sufficient.

     

    http://www.h-online.com/newsticker/news/item/Secure-deletion-a-single-overwrite- will-do-it-739699.html

     

    FYI: from my experience, a single pass of a 500GB drive will take around 2.5-3+ hours, depending on the processor speed and the drive. That was with FW400. If it's a USB external, it will be quite a bit slower.

     

    Message was edited by: WZZZ

  • Michael Wasley Level 5 Level 5 (6,810 points)
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    Feb 21, 2013 2:16 PM (in response to seventy one)

    seventy one wrote:

     

    The disk was holding 150 GB.

    Do you mean that was the used space or the total capacity? I'm guessing you mean the former. As varjak paw has said the whole disk will be erased - so what's the capacity of the drive?

     

    Curiosity makes me ask why you chose the seven pass option in the first place?

  • Klaus1 Level 8 Level 8 (43,430 points)
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    Feb 21, 2013 3:18 PM (in response to seventy one)

    seventy one wrote:

     

    Okay Klaus1, give us a figure.   Hint.   It's now gone out to 1 day and 19 hours.

    The first of your seven passes is about half-way completed.

     

    Should be finished by Easter!

  • BobHarris Level 6 Level 6 (12,510 points)
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    Feb 21, 2013 8:06 PM (in response to seventy one)

    I'm on pass 2 of 7

    ...

    can I stop it and restart using a 1 pass?

    You can just stop peroid.  You have written 2 passes of random data which is going to make figuring ouit what was originally on the disk extremely possible to detect.

     

    If you still want to write zeros, then restart with a single pass of zero.

  • WZZZ Level 6 Level 6 (11,880 points)
    Currently Being Moderated
    Feb 21, 2013 8:17 PM (in response to seventy one)

    As Bob said, you can stop right now and feel very confident no one's going to get at your data. Absolutely no need for another pass of zeros.

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