What is the difference between empty trash & secure empty & will it affect my SSD?

Discussion in 'MacBook Pro' started by clutchm3, Aug 24, 2011.

  1. macrumors regular

    Joined:
    Aug 9, 2011
    #1
    Hey guys what is the difference between empty trash & secure empty & if I secure empty the trash will it affect my SSD? It certainly takes longer. :confused:
     
  2. macrumors regular

    Joined:
    Nov 1, 2006
    #2
    simple delete just really 'unlinks' the file from directory/folder/filesystem entries, but does not really delete the file, just referencess to it/ways to access it.

    secure deletion actually overwrites the deleted file with random data before doing the above. I don't recall if secure empty trash does a single pass over the file or 7. The US government/DOD/etc. generally requires a 3 pass overwrite to consider data to be truly wiped.

    So, it's up to you - use normal delete, and it's not difficult to buy or write a program that can recover the original files, but if you aren't worried about the laptop or data winding up stolen or in someone elses hands, or if you are constantly adding and deleting data and keep your drive near capacity, it's not that big of a deal.

    A single pass or more of random overwrite is going to ensure most available programs (that I'm aware of, anyways) are not going to be able to recover your deleted data at all. A single pass *may* be recoverable by data recovery experts charging insane $, and multiple passes makes recovery *almost* to possibly entirely impossible regardless of who is trying to recover it.

    Obviously, a simple directly/file 'unlink'/entry removal - nearly instant, and any of the overwrite/secure methods are significantly longer, and will be longer based on the number of passes made.

    Can anyone confirm the number of passes made by 'secure empty trash'? It' using 'srm' under the covers, so easy enough to test I suppose..better would be if there's a way to change the number of passes made by secure empty trash - anyone know a setting or plist entry on that one?

    Oh, PS - secure empty trash will be doing significantly more writes to a disk (or SSD) than normal deletion does. SSDs are generally rated at least years of usage, but it depends on how accurate vs how much you're writing to it, up to you - you can look up the numbers of writes estimated for specific SsDs before failure if you'd like.
     
  3. macrumors 65816

    awer25

    Joined:
    Apr 30, 2011
    #3
    Just use regular delete - it's a lot faster and better for your SSD. If you really are worried that someone will recover your files, then once in a while (like overnight when you're not using the computer) open Disk Utility and "Erase Free Space". That will do the same thing.
     
  4. 3bs
    macrumors 603

    3bs

    Joined:
    May 20, 2011
    Location:
    Dublin, Ireland
    #4
    How is it bad for the SSD if you secure empty the trash every time?
     
  5. macrumors 65816

    awer25

    Joined:
    Apr 30, 2011
    #5
    "how bad" is a subjective term. It's better to have less writes on the SSD, so extra writes are therefore worse. How much so...I have no idea.
     
  6. macrumors 68040

    dusk007

    Joined:
    Dec 5, 2009
    #6
    If you really have some very sensitive files just empty the bin first. Throw those files in an do a secure erase.
    It is not such a big deal for the SSD life expectancy but it really is a waste of time for anything but important files that need shredding.

    BTW. Even a single overwrite is according to research enough to make in practically impossible for pretty much anyone to recover those files. Some bits can be recovered with some luck and really really expensive equipment but the recovering of a couple thousand bits that make up even small files is close to impossible. Multiple overwrites are just to be sure but it really isn't necessary for anybody who doesn't hold secrets that are worth a couple million $.
     
  7. Hyper-X, Sep 6, 2011
    Last edited: Sep 6, 2011

    macrumors 6502a

    Joined:
    Jul 1, 2011
    #7
    Empty trash simply tells the OS to mark the area occupied by the files that are to be deleted as available space. It would be no different from you occupying room 10 in a motel with someone placing an "open vacancy" sign on your door despite you still being inside. As you can see the data is still there and recoverable, however if the OS chooses to, it can overwrite where the data currently is.

    Secure Empty is a method in which the OS tries to encrypt the area where your data resides so that recovery will be less successful. This is similar to shredding your papers before it goes into the trash bin, or taking a permanent ink marker and scratching out all the readable content on your paperwork several times and such.

    However with a SSD, the actual performance of Secure Empty is significantly worse than you might think. Check the following link for more details as to how it's still able to recover up to 67% of your data on a SSD even after you use Secure Empty.

    http://www.zdnet.com/blog/storage/mac-fail-ssd-security/1293
     

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