Just got a macbook air, 13 inch... hard drive capacity?!?

Discussion in 'MacBook Air' started by bender644, Aug 4, 2011.

  1. bender644 macrumors member

    Feb 23, 2008
    Hi guys,

    I just got the 128gb model. It says, when I check the info on my hard drive that it has a capacity of "120.47gb" (why?) and has only 106.76gb of available space. I understand that the OS takes up space, along with other programs and such, but how does it go down from 128 to nearly 120?

    Where does the OS come in? I'm very surprised that, right as I turned it on I only have ~107 gb of space.

    Can you guys explain this?

    Thanks for your input.

  2. KPOM macrumors G5

    Oct 23, 2010
    SSDs reserve a certain amount of space called "overprovisioning" to reduce wear. In short, because the drive can only be written to and read a finite number of times, the drive "sets aside" an amount that isn't available for use. Over time, it moves data to the "set aside" space, and then marks the older space as unavailable.

    The 128GB drives have a usable capacity of 121GB as a result. The 256GB drives have a capacity of 251GB, so they are actually slightly more than twice the size.
  3. artivideo.nl macrumors 6502

    Jan 10, 2008
    The Netherlands
    "reduce wear" it is an SSD. I know that their lifetime is not infinite (like a Panasonic P2 card, except for the silver type) but the number that a particular place on the SSD is overwritten is so small that you can consider it as infinite.

  4. bender644 thread starter macrumors member

    Feb 23, 2008
    Thanks for the explanation. I know that SSD have a finite number of writes, and of course on the Macbook Air, eventually you'd have to toss it since the drive itself has been soldered onto the motherboard.

    But, this finite number of times must be super high, so much so that you'd really not have to worry about it. I assume by the time, if ever, it became an issue you'd probably be getting a new computer.

    So then, on a regular hard drive I'd actually be getting more space? I was surprised at the amount that is left in the end...but, I am overall super happy.

    BTW, on a side note, still trying to decide if I should get the apple care plan for the MBA....how much does it cost to replace the battery on these things?
  5. DeusInvictus7 macrumors 68020

    Aug 13, 2008
    Kitchener, Ontario
    The drive isn't soldered onto the board. It's just a custom form factor so no normal SSD will work.

    So far, only OWC sells upgraded Sandforce based SSDs for the MBA.
  6. The Catalyst macrumors 6502

    Dec 4, 2009
    side note question -- if you were to open up your Air and upgrade the SSD, do you loose the TRIM support?
  7. DeusInvictus7 macrumors 68020

    Aug 13, 2008
    Kitchener, Ontario
    I think so, but Sandforce drives take care of themselves quite well with just the controller, so I honestly wouldn't worry about it too much.

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