Previous 1 2 Next 18 Replies Latest reply: Feb 22, 2013 12:42 AM by seventy one
seventy one Level 6 Level 6 (10,405 points)

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)
  • seventy one Level 6 Level 6 (10,405 points)

    Bump.   Would anyone have an idea?

  • Klaus1 Level 8 Level 8 (45,360 points)

    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 (169,820 points)

    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 (45,360 points)

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

  • seventy one Level 6 Level 6 (10,405 points)

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

  • seventy one Level 6 Level 6 (10,405 points)

    Not sure you formulae is on target.   Since your post it has now gone out to 2 days!

  • varjak paw Level 10 Level 10 (169,820 points)

    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 (12,640 points)

    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)

    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 (45,360 points)

    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!

  • seventy one Level 6 Level 6 (10,405 points)

    Thank you Michael, WZZZ and Varjak paw (again).

     

    Okay.   There seems a concensus forming.   The drive is a Lacie 500 GB used for Time Machine.   The 150 GB is what had been used.  

     

    I have to admit I chose the 7 pass option because I do tend to be over cautious in these matters.   It did ponder how much longer it would take and wasn't overly bothered when the first time estimate showed up as 16 hours.   But as time passed and the estimate rose from 1 day to 2 days (currently 2 days 2 hours).   I suppose best policy would be to leave it running, and report back in 2 days time if things look no better; as of now it has been running for 10 hours and I'm on pass 2 of 7.

     

    Most grateful to everyone who is contributing; any further observations would be equally appreciated.

  • seventy one Level 6 Level 6 (10,405 points)

    As will the chocolate bunny rabbit.   Can't help but smile    It crosses my mind  ...  can I stop it and restart using a 1 pass?

  • BobHarris Level 6 Level 6 (14,720 points)

    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 (12,640 points)

    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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