SSD formatted capacity 55.5GB??

Discussion in 'MacBook Air' started by whozurdaddy, Feb 4, 2008.

  1. whozurdaddy macrumors newbie

    Feb 4, 2008
    Are we getting short changed? On Apple's site ( for the Optional 64GB solid-state drive at the bottom of the page it states that "1GB=1 billion bytes. Actual formatted capacity less."

    So by this math, 64GB = 64,000,000,000 bytes. If you convert that gigabytes it should be 59.6GB. Why is the capacity in Disk Utility showing 55.5GB? Is this a 60GB SSD drive? I know people have complained about similar issues before (see here: but I don't understand the 4GB discrepancy (59.6GB vs 55.5GB).
  2. switz macrumors member

    Jan 16, 2008
    East edge of Phoenix urban sprawl
    I am typing this on my new 1.8 SSD I bought at the Chandler Apple store in Phoenix. It was the last of the ten units that came in today. The 64Gb is probably a marketing number. One typically looses at a minimum of 7% to 15% of the space when formatting the device. If we do the division, we see about 13% overhead which is not that unreasonable.

    The unit I had on order with the Apple store may not get out of Shanghai Pudong airport may not depart until next week due to both the Chinese New Year celebrations and the severe weather. As I will on the road, I elected to acquire the available unit. One in hand is worth two in the bush.

    In the time it took to type this the little fan has come on. I think it has been busy downloading updates while I was composing this message.
  3. whozurdaddy thread starter macrumors newbie

    Feb 4, 2008
    First, congrats on your new system! I ordered mine from and it cleared customs on 2/3. I have yet to hear my fan come on, but I'm not really doing a whole lot yet.

    As for the space, 64GB is a marketing number but even using their math it doesn't add up. I understand slack space and how cluster sizes can affect the available free space, but we're talking about the raw numbers from Disk Utility.

    It's all math. We should be able calculate exactly how much raw disk space is available and by numbers, it's off my 4GB.
  4. whozurdaddy thread starter macrumors newbie

    Feb 4, 2008
  5. michaelvoigt macrumors member

    Nov 13, 2007
    lost space could be Mac OS X swap partition

    Does OS X use a dedicated swap partition? if that is the case that could account for the lost space that you see?
  6. jahala macrumors regular


    Feb 7, 2008

    I know that there is a small partition for EFI data, but I don't know how big it is.
  7. xUKHCx Administrator emeritus


    Jan 15, 2006
    The Kop
    IIRC it is 200MB.
  8. aristobrat macrumors G5

    Oct 14, 2005
    Could the EFI (i.e. recovery partition) be larger in order to deal with the AirDisk method of being able to restore the OS via WiFi?
  9. thejadedmonkey macrumors 604


    May 28, 2005
    4 gigs is enough space for an entire OS!
  10. aristobrat macrumors G5

    Oct 14, 2005
    Yeah, that's true. When I googled this topic, I saw an HP document that stated up to 8GB on a SSD drive could be dedicated to system recovery, so I wasn't sure if they were specifically talking about how they do SSD drives, or SSD drives in general.

    This was interesting. I wasn't aware that there was a maximum amount of times that a SSD could be written to (not that a normal person would ever run into that). Wonder if there's some disk space kept in reserve for problems with cells?,1
  11. Krevnik macrumors 68040


    Sep 8, 2003
    All good drives do. Even HDDs you buy now have reserve blocks which are only used when bad blocks are found. But it doesn't affect the actual formatted capacity (The advertised space for an HDD doesn't include the reserve blocks).

    I don't know why there is still a 4GB block of space unaccounted for. That is a bit big to be used for reserve blocks.
  12. cowm007 macrumors regular

    Feb 2, 2005
    Open up terminal and type in "diskutil list". Maybe there's a hidden partition in there?
  13. redbma macrumors newbie

    Oct 1, 2002
    Have the same 'issue' here. Got my 1.8/64SSD MBA yesterday and noticed the reduced capacity. Diskutil results were:

    0: GUID_partition_scheme *55.9 Gi disk0
    1: EFI 200.0 Mi disk0s1
    2: Apple_HFS Macintosh HD 55.6 Gi disk0s2

    Doesnt seem to shed any more light on where the missing 4GB ended up.

    Anyone tried doing a reformat and reinstall?
  14. txlef macrumors newbie

    Feb 8, 2008
    My diskutil list shows the same thing:

    0: GUID_partition_scheme *55.9 Gi disk0
    1: EFI 200.0 Mi disk0s1
    2: Apple_HFS Macintosh HD 55.6 Gi disk0s2

    I'm feeling kind of ripped off.
  15. cowm007 macrumors regular

    Feb 2, 2005
    Yea, looks like the actual disk is 55.9 gb and not just the system partition. Diskutil's output indeed shows that the disk is just 56gb, so there's no hidden OS partition or anything (Also unlikely since a Leopard install disk is around 7gb).

    For comparison purposes, I have a 500GB hard drive, but the actual size is about 465GB which makes sense once you do the math:
    Marketing GB = 1,000,000,000 bytes
    Real GB = 1,073,741,824 bytes (1024 B in a KB, 1024 KB in a MB, 1024 MB in a GB)

    Marketing Capacity = 500,000,000,000 bytes
    Real capacity = 465,660,000,000 bytes (500,000,000,000 / 1,073,741,824)

    So 56gb from 64 is kinda sketchy. Especially when you're paying such a premium for the SSD drive. Why must they continue with these B.S. games of 1000 vs 1024 bytes to describe sizes?
  16. acfusion29 macrumors 68040


    Nov 8, 2007
    So Safari, Mail, iChat, Calendar, iTunes etc. are supposed to take up no space? :rolleyes:

    That 4GB went towards the OS and the Apps installed.
  17. cowm007 macrumors regular

    Feb 2, 2005
    I hate to say it, but the drive's actual capacity would be quoted by the manufacturer as 60Gb instead of 64Gb when using the 1,000,000,000 bytes per gigabyte conversion. So something's definitely strange and worth calling Apple about.
  18. whozurdaddy thread starter macrumors newbie

    Feb 4, 2008
    I've done a reinstall (using the sticky here). The starting capacity of the drive is 55.9 GB.

    I really do think there's something to this. I posted a message on Apple here), but I didn't really get anywhere.
  19. xUKHCx Administrator emeritus


    Jan 15, 2006
    The Kop
    I'd phone apple about this and see what they have to say.
  20. Beliyaal macrumors member

    Feb 14, 2008
    The plot thickens. In the anandtech review his Samsung disk not purchased from Apple has 59.63 GB Capacity and is formatted to 59.31 GB. What do you see in your system profile?

    Check screenshot at the bottom of the page
  21. ayeying macrumors 601


    Dec 5, 2007
    Yay Area, CA
    I noticed this at the stores too. The MacBook Air's SSD drive is only 55.9GB, which is bascially a 60GB hdd (55.9GB usable)
  22. lewisozz macrumors member


    Feb 2, 2008
    United Kingdom
    Omg !!!!!

    That bad of apple to advertise a fake size of the HD or SDD !!!! Why cant they show the real size of the HD or SSD !!!!:apple::mad:
  23. ViperrepiV macrumors regular

    Jan 25, 2008
  24. whozurdaddy thread starter macrumors newbie

    Feb 4, 2008
    Good find Beliyaal!

    It's definitely a different drive. My drive is listed as a MCCOE64GEMPP with a capacity of 55.9 GB and Anand's is a SAMSUNG PZA064 SSD with a capacity of 59.63 GB.


    I'll call Apple tomorrow. I don't want to whine here, but this is BS. Every gig counts when you're talking about an SSD drive. I paid for a 64GB drive and Apple sold me a 60GB drive.
  25. profiteor macrumors member

    Jan 31, 2008
    From the Samsung Semiconductor info page on the MBA drive:

    Drive Capacity
    Unformatted Capacity 64GB
    User-Addressable Sectors 125,045,424
    Bytes per Sector 512

    = 59.63GiB (powers of 2 GB, what your OS sees)

    There's an Apple Diagnostic Test accessible via D at boot without using the DVD... but I'm sure that either lives in EFI or the EFI partition. Very small. Not 4GB. Makes me wonder if Apple implemented a 10% rewrite area, or something.

    OS X does not use a swap partition.

    Half tempted to hack into EFI and see what it thinks of the drive.

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