Just started using 1TB Time Capsule but 929.5GB?

Discussion in 'Mac Accessories' started by J22, May 15, 2008.

  1. J22 macrumors newbie

    May 15, 2008
    When I just started the Time Machine on Time Capsule, I noticed available space is 929.5GB. Is that normal? That's at least 90GB subtract from 1TB.

  2. Tallest Skil macrumors P6

    Tallest Skil

    Aug 13, 2006
    1 Geostationary Tower Plaza
    Welcome to the world of hard drive manufacturing. The companies make their drives with 1 terabyte = 1000 gigabytes in mind, but all software is written to understand that 1 terabyte = 1024 gigabytes.
  3. cdrtravis macrumors newbie

    May 8, 2008
    Yep. Perfectly normal. No drive ever formats to the physical capacity stated by the manufacturer. There are also mathematical reasons, which have caused a long running debate as to whether hard drive manufacturers are ripping consumers off or not.
  4. motulist macrumors 601


    Dec 2, 2003
    The actual capacity will be lower than the advertised capacity due to the BS math that all hard drive capacities are advertised as from all manufacturers.

    However, if your hard drive really is spic-n-span clean and empty, your number does seem lower than the BS math would result in.

    929.5 * 1.024 = 951.8

    So you should have 951.8 GB of usable capacity, so it seems as if you're about 22 GB below what should theoretically be available.

    p.s. Gosh I'm old, I kept writing MB in those numbers instead of GB because my brain just isn't ready to assume that large numbers like these could possibly be values in GIGAbytes, not megabytes. And by the time my mental default adjust it'll probably be about time when many hundreds of terabytes becomes the norm. Oh well, whatta ya gonna do.
  5. J22 thread starter macrumors newbie

    May 15, 2008
    Ah, ok... thanks for the quick answers. I should have done this a month ago before my old 100GB hard drive crashed and lost everything.

  6. flopticalcube macrumors G4


    Sep 7, 2006
    In the velcro closure of America's Hat
  7. Chundles macrumors G4


    Jul 4, 2005
    It's all binary's fault.

    The standard definition of a kilo-anything is 1000 of that thing, binary came along and couldn't deal in powers of ten, only powers of two. So they decided that "near enough was good enough" and that 1024 bytes should be called a "kilobyte" despite there being 24 more bytes than the SI definition allows for.

    Well, in those days of kilobytes the extra 24 bytes meant SFA but now that we're in the realm of terabytes it's really starting to add up.

    Manufacturers are adhering to the rule, when you buy a terabyte HDD you are getting 1,000,000,000,000 bytes of storage but the computer's wacky idea of a kilobyte comes in to ruin your party.

    1 000 000 000 000 / 1024 = 976 562 500 supposed kilobytes
    976 562 500 / 1024 = 953 674 supposed megabytes
    953 674 / 1024 = 931 supposed gigabytes

    So you're only missing 1.5"GB" for formatting etc. Looks fine to me.

    In reality you're getting the full 1000000000000 bytes you paid for, minus a little bit for formatting.

    The kilobyte problem so long ago now means that there's about a 7% discrepancy between the bytes you buy and the "gigabytes" your computer tells you that you have.
  8. motulist macrumors 601


    Dec 2, 2003

    So if I'm understanding you correctly you're saying that instead of doing

    [advertised capacity] * 1.024

    like I used to do in the old days, these days I have to do

    [advertised capacity] * 1.072

    Lets check it out against his numbers:

    929.5 * 1.072 = 996.3

    Yup, that looks about right.

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