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Michael710

Q: Zero Out Hard Drive Question

I have been using my 27" iMac for various software testing. Now that my testing is complete I want to wipe the drive and start fresh. In Disk Utility there are many options to choose from when going to Erase > Security Options. Is there any benefit to Zeroing out the drive before re-installing Snow Leopard? Or can I just select the Don't Erase Data option and reinstall deleting the home folder when prompted. Does Zeroing out free any more space up?

MacBook Pro 2.8 Anti-Glare, Mac OS X (10.6.1), Kingston 256 GB V+ Solid State Drive

Posted on Mar 9, 2010 12:53 PM

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Q: Zero Out Hard Drive Question

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  • by The hatter,

    The hatter The hatter Mar 9, 2010 12:58 PM in response to Michael710
    Level 9 (60,935 points)
    Mar 9, 2010 12:58 PM in response to Michael710
    Erase the drive, not the partition. That way you are starting fresh. And leave the zero data for secure erase of just that, data.

    In theory zero all might find weak or bad blocks but there are better tools, and better uses of your time.

    Start using backup images and clones of your system. SuperDuper can also help 'sandbox' your system for testing purposes. No reason to have just one boot drive.
  • by Michael710,

    Michael710 Michael710 Mar 9, 2010 1:01 PM in response to The hatter
    Level 1 (10 points)
    Mar 9, 2010 1:01 PM in response to The hatter
    So what you are saying is click on the Parent (Top-Level) in the tree and select Erase. Will that not just erase everything anyways?
  • by baltwo,

    baltwo baltwo Mar 9, 2010 1:05 PM in response to Michael710
    Level 9 (62,256 points)
    Mar 9, 2010 1:05 PM in response to Michael710
    There is no benefit to zeroing out the HD unless you want to prevent the current data from being recovered and, unless you're dealing with national security information, it's a waste of time.
  • by The hatter,

    The hatter The hatter Mar 9, 2010 1:05 PM in response to Michael710
    Level 9 (60,935 points)
    Mar 9, 2010 1:05 PM in response to Michael710
    Yup, totally. Nothing left - 'course you have to be booted from another device.

    And when testing, hope you have good backups.
  • by Michael710,

    Michael710 Michael710 Mar 9, 2010 1:16 PM in response to The hatter
    Level 1 (10 points)
    Mar 9, 2010 1:16 PM in response to The hatter
    Sorry sometimes I am not clear...

    So right now I have Snow Leopard installed if I go into Disk Utility I see the following:

    1 TBST31000528ASQ Media
    -Macintosh HD

    If I boot from the Snow Leopard CD and select Utilities > Disk Utility and select 1TB ST31000528ASQ Media then click Erase (option Security Options > Don't Erase Data) does this erase all the data in the Hard Drive?

    Am I losing any space by not zeroing out?

    Will the space that had Snow Leopard previously installed just be "re-used?"

    What is the difference if I select Macintosh HD versus 1TB ST31000528ASQ and erase?

    I do not have a SSD, I am using a stock i5 iMac. Sorry for the incorrect signature.

    Message was edited by: Michael710
  • by KJK555,

    KJK555 KJK555 Mar 9, 2010 1:15 PM in response to Michael710
    Level 4 (2,895 points)
    Mar 9, 2010 1:15 PM in response to Michael710
    I notice you have a solid state drive. Unless you have top secret or important sensitive information
    on your drive, don't do it, all you are doing is reducing the life of your SSD.

    If your machine does have a regular drive, then unless the data needs to be wiped for security
    purposes, a single pass "0" wipe is more than sufficient to do the job.


    Kj ♘
  • by V.K.,

    V.K. V.K. Mar 9, 2010 1:27 PM in response to Michael710
    Level 9 (56,110 points)
    Mar 9, 2010 1:27 PM in response to Michael710
    Michael710 wrote:
    I have been using my 27" iMac for various software testing. Now that my testing is complete I want to wipe the drive and start fresh. In Disk Utility there are many options to choose from when going to Erase > Security Options. Is there any benefit to Zeroing out the drive before re-installing Snow Leopard?

    no, there is no benefit to this at all. zeroing out is only needed to prevent data recovery. it serves no other function. apparently, it doesn't even map out bad blocks on the hard drive.
    Or can I just select the Don't Erase Data option and reinstall deleting the home folder when prompted.

    "don't erase data"?? there is no such option in disk utility. just erase the drive using the erase tab. this will erase everything on your hard drive. or better yet, reformat the drive using the partition tab. then quit disk utility and proceed with the install.

    Message was edited by: V.K.
  • by Michael710,

    Michael710 Michael710 Mar 9, 2010 1:28 PM in response to V.K.
    Level 1 (10 points)
    Mar 9, 2010 1:28 PM in response to V.K.
    Thanks everyone for your help... Question answered. V.K., there is an option under Security Options. It is right above Zero Out Data.
  • by Michael710,

    Michael710 Michael710 Mar 9, 2010 1:29 PM in response to Michael710
    Level 1 (10 points)
    Mar 9, 2010 1:29 PM in response to Michael710
    Thanks!
  • by baltwo,

    baltwo baltwo Mar 9, 2010 2:41 PM in response to Michael710
    Level 9 (62,256 points)
    Mar 9, 2010 2:41 PM in response to Michael710
    The "do not erase data" option is the default when erasing, which just wipes the volume's directory. When you select one of the write zero options, that overwrites the data with zeros. Hope that clears up the confusion.
  • by Michael710,

    Michael710 Michael710 Mar 9, 2010 2:48 PM in response to baltwo
    Level 1 (10 points)
    Mar 9, 2010 2:48 PM in response to baltwo
    It does, but that is my concern, if I do not Zero out the data, will it eventually get overwritten with the re-install?
  • by baltwo,

    baltwo baltwo Mar 9, 2010 3:05 PM in response to Michael710
    Level 9 (62,256 points)
    Mar 9, 2010 3:05 PM in response to Michael710
    Yes. Exactly like what happens whenever you delete a file. Only its directory pointer gets wiped, not the actual data. Subsequent writes to the disk overwrite it. There's nothing to be concerned about. It doesn't matter what's currently on the HD, zeros or anything else, subsequent writes will overwrite the bits.