AirPort showing different Time Capsule disk capacity than Time Machine

Discussion in 'macOS' started by PatriotInvasion, Sep 8, 2010.

  1. PatriotInvasion macrumors 65816

    PatriotInvasion

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    #1
    So I just secure erased my Time Capsule disk through AirPort Utility to set it up with my new iMac. After erasing the 1TB disk, AirPort said that the disk capacity is only 931GB even though the Time Machine preferences displayed 998GB available prior to me initiating the first backup.

    Does anyone know why this discrepancy exists?

    It should be noted that the previous backup on the Time Capsule disk from my old Mac took up about 68GB so is AirPort Utility just struggling to show the new capacity after the secure erase?:confused:

    Please help!
     
  2. AppleNewton macrumors 68000

    AppleNewton

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    #2
    I presume you're using OS X 10.6.x (Snow Leopard)?

    The problem is that, the OS shows the 'total' value of the drive space in the Base10 calculated format (http://support.apple.com/kb/ts2419); while for some reason the 'AirPort' (AEBS, TimeCapsule) devices show the Binary System (Base2) calculated size of the drive space.

    Because my 2TB time capsule in AirPort Utility shows it as 1.8TB, however OS X Finder and Time Machine see it as 2TB.
     
  3. PatriotInvasion thread starter macrumors 65816

    PatriotInvasion

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    #3
    I understand but this is not a discrepancy of 2 or 3GB's. My Time Machine preferences show that 930GB of 998GB is free while AirPort is saying just 862GB of 931GB is free on the same disk! It's off by over 60GB.

    When I did a secure erase of the Time Capsule disk prior to initiating my first backup, AirPort seems to have not reset the max capacity of the drive back to 1TB (or 998GB). Any other ideas?

    PS - Yes I am running the absolute latest version of everything - Snow Leopard included.
     
  4. cube macrumors G5

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    #4
    (2 ^ 30) * 930 = 998579896320
    (2 ^ 30) * 931 = 999653638144
    (2 ^ 30) * 932 = 1000727379968
     
  5. AppleNewton macrumors 68000

    AppleNewton

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    #5

    Well you didnt really mention that in your post other than saying its showing 931 in AirPort (which would be accurate) and 998 in Snow Leopard (~accurate).

    There seems to be an issue with the TimeCapsule then, if nothing else.
    I would connect it via ethernet and try another secure erase and a total restore of the TimeCapsule itself to eliminate any other possibility of error.

    Then in finder navigate to the harddrive on the timecapsule to make sure no files are there.
     
  6. PatriotInvasion thread starter macrumors 65816

    PatriotInvasion

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    #6
    I was thinking of just doing a full reset of the Time Capsule (which will likely solve the problem), but I'll have to recreate my wireless network and everything just so the numbers match up.

    There are no other files on the disk other than the sparsebundle that was created from the first backup. Strange...It's almost as if AirPort thinks the previous space available was the actual capacity of the disk even after I did a full erase of the disk.
     
  7. cube macrumors G5

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    #7
    It's not off by 60GB. The free space is off by about 4GB, according to the numbers you showed.
     
  8. cube macrumors G5

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    May 10, 2004
    #8
    There could be a difference in the reporting of the size of files using HFS compression.
     
  9. PatriotInvasion thread starter macrumors 65816

    PatriotInvasion

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    #9
    What do you mean. This is what i said:

    My Time Machine preferences show that 930GB of 998GB is free while AirPort is saying just 862GB of 931GB is free on the same disk! It's off by over 60GB.

    930-862=68GB
     
  10. willieva macrumors 6502

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    Mar 12, 2010
    #10
    They're both showing 93% full in their respective measuring units.

    Computer manufacturers nowadays are starting to quote things in terms of billions of bytes, as opposed to gigabytes. A gigabyte is 2^30, or 1073741824 bytes. A billion bytes is 100000000 bytes. So one number is in billions of bytes, the other gigabytes.
     
  11. PatriotInvasion thread starter macrumors 65816

    PatriotInvasion

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    #11
    So are you saying that AirPort reporting 931GB of capacity for a 1TB Time Capsule is correct? I don't know what number was shown when I first set it up (may have been 931GB from the start, but not sure)...:confused::confused::confused:
     
  12. cube macrumors G5

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    #12
    The Airport label is wrong. It's not 862GB, it's 862GiB.
     
  13. PatriotInvasion thread starter macrumors 65816

    PatriotInvasion

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    #13
    I don't know what that means
     
  14. cube macrumors G5

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    #14
    I did the computation for you above.

    Again, it should use GiB labels, not GB.

    GiB was invented to avoid the misuse of GB.
     
  15. willieva macrumors 6502

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    #15
    What I'm saying is one system is calling a gigabyte 10^9 bytes. The other is saying a gigabyte is 2^30. If you do the math:
    10^9 / 2^30 = 931 / 998

    The ratio of sizes reported is equal to the ratio between 10^9 and 2^30.
     
  16. PatriotInvasion thread starter macrumors 65816

    PatriotInvasion

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    #16
    Ok, so AirPort is showing the correct number despite the GB vs GiB designation??? So even if I completely reset the Time Capsule to it's factory settings, it will still report the same number and won't display the 998GB capacity number that Time Machine Preferences shows me during a backup?
     
  17. cube macrumors G5

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    May 10, 2004
    #17
    Yes, the Airport number is correct, in gibibytes (2 ^ 30)

    Snow leopard shows gigabytes (10 ^ 9)

    That's the way they always display.

    Previous versions of OSX showed mislabeled gibibytes, like the Airport.
     
  18. PatriotInvasion thread starter macrumors 65816

    PatriotInvasion

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    #18
    Ok, fair enough. I appreciate everyone's help with this. Not sure why Apple wouldn't be consistent within applications that they created, but as long as everything is being reported correctly in their own way, I'm fine.:) Thanks again.
     
  19. cube macrumors G5

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    May 10, 2004
    #19
    It doesn't even mean that everything in Snow Leopard will use conventions consistently: legacy command-line programs, 3rd-party applications, etc.

    You have to know how each piece of software is reporting. You can only be sure when a program uses KiB, MiB, GiB, TiB, etc.
     

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