Sticky Hard drive showing wrong capacity? Here's why.

Discussion in 'Computer Hardware' started by HAL9000, Dec 8, 2004.

  1. HAL9000

    HAL9000

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    Since we get numerous threads on this subject, I thought I would post this and sticky it.. hope it helps understand why hard drives don't format to their advertised capacity.

    Determining drive capacity can be confusing at times because of the different measurement standards that are often used. When dealing with Windows and Mac based systems, you will commonly see both decimal measurements and binary measurements of a drive's capacity. In either case, a drive's capacity is measured by using the total number of bytes available on the drive. As long as the drive displays the correct number of bytes (approximate), you are getting the drive's full capacity.

    Decimal vs. Binary:
    For simplicity and consistency, hard drive manufacturers define a megabyte as 1,000,000 bytes and a gigabyte as 1,000,000,000 bytes. This is a decimal (base 10) measurement and is the industry standard. However, certain system BIOSs, FDISK and Windows define a megabyte as 1,048,576 bytes and a gigabyte as 1,073,741,824 bytes. Mac systems also use these values. These are binary (base 2) measurements.

    To Determine Decimal Capacity:
    A decimal capacity is determined by dividing the total number of bytes, by the number of bytes per gigabyte (1,000,000,000 using base 10).

    To Determine Binary Capacity:
    A binary capacity is determined by dividing the total number of bytes, by the number of bytes per gigabyte (1,073,741,824 using base 2).
    This is why different utilities will report different capacities for the same drive. The number of bytes is the same, but a different number of bytes is used to make a megabyte and a gigabyte. This is similar to the difference between 0 degrees Celsius and 32 degrees Fahrenheit. It is the same temperature, but will be reported differently depending on the scale you are using.



    --------------------------------------------------------------------------



    Various Drive Sizes and their Binary and Decimal Capacities



    Drive Size in GB Approximate Total Bytes Decimal Capacity
    (bytes/1,000,000,000)
    Approximate Binary Capacity (bytes/1,073,724,841)
    10 GB 10,000,000,000 10 GB 9.31 GB
    20 GB 20,000,000,000 20 GB 18.63 GB
    30 GB 30,000,000,000 30 GB 27.94 GB
    40 GB 40,000,000,000 40 GB 37.25 GB
    60 GB 60,000,000,000 60 GB 55.88 GB
    80 GB 80,000,000,000 80 GB 74.51 GB
    100 GB 100,000,000,000 100 GB 93.13 GB
    120 GB 120,000,000,000 120 GB 111.76 GB
    160 GB 160,000,000,000 160 GB 149.01 GB
    180 GB 180,000,000,000 180 GB 167.64 GB
    200 GB 200,000,000,000 200 GB 186.26 GB
    250 GB 250,000,000,000 250 GB 232.83 GB

    ----------------------------------------------------------------------------------------------------------------

    Please note his thread is NOT FOR INDIVIDUAL QUESTIONS - please start your own thread if this sticky does not answer your question - but is open for discussion if anyone has anything to add.
     
    Last edited by a moderator: Nov 18, 2008
  2. easg

    easg

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    I readed a forum thread, and someone posted that that difference was beside the explanation above, because the FAT uses some HD space.
     
  3. WhatsThisBoxFor?

    WhatsThisBoxFor? PCMech: Saving Lives

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    Also, another common reason why harddrives do not show up the right capacity:
    FAT16 File system: Max 2GB partitions (I think this counts FDisk with no large disk support)
    FAT32 (on Win9X): 2 TB (Terrabytes)
    FAT32 (on Win2000 and XP): 32Gb
    NTFS (Pre SP1 installer): 127GB (or there abouts.)
    NTFS (SP1 or higher): 2 TB

    You also have to check BIOS constraints, and maybe update to a newer versions. Many very, very old BIOS's can't go above 8GB (or even 2Gb in some cases), and some older ones have a ~32GB limit. Some boards also hit rock bottom at about 128GB.

    So what of your BIOS doesn't support large harddrives? It is possible to fit a controller card, which can get around these problems. But even using a controller card, windows limits also apply.

    Without using a controller card, you can install a BIOS overlay, but these can lead to other problems with harddrives, and are not generally recomended. If you are in doubt, you can always ask here.

    Great Thread Hal, just thought I would share other harddrive capacity problems I have experienced.
     
  4. HAL9000

    HAL9000

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    The file allocation table is minimal.... it's all in the math why the differences exist.
     
  5. Force Flow

    Force Flow Barefoot on the Moon! Staff Member

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    First, FAT16 file systems can only see partitions that are less than 2GB, and Windows 98 has a limiting partition size of 137GB. Anything larger, and it just doesn’t exist as far as the host machine is concerned. There are really no workarounds for these two limitations. The issue with older machines is that no matter what file system is being used, the motherboard’s BIOS may not support large capacity partitions. Yes, this hardware limitation carries over to Unix/Linux platforms, not being a software issue. There are partition limits with older BIOS chips: 137GB, 32GB, 8GB, 2GB, and 504MB, depending on the age and the type of BIOS. This leaves you a few ways to get around this limiting factor. One workaround is to install a PCI IDE card (with SATA capabilities, if needed). The other is to simply use a newer machine. A riskier third option would be to see if a newer BIOS revision was released that fixes the limitation, and to perform a BIOS flash with this update. If done incorrectly, the BIOS flash can effectively render your motherboard useless. There is one exception to the partition limitation you should be aware of among modern systems: note that if you are running Windows XP without SP1 (Service Pack 1), there is a software limitation of seeing partitions larger than 137GB. Installing SP1 fixes this issue. Windows 2000 has a similar issue with the 137GB limitation, but if you have either SP3 or SP4, the problem will be resolved. Anything lower than SP3, and you’re stuck with the 137GB limit.

    ~From the Data Recovery article
     
  6. ric449

    ric449

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    Remember there is a limitation with anything below ATA100 too. Anything below ATA100 can only support 137GB, it is a hardware limitation. The only way of getting around it is to install a controller card or get a new motherboard.
     
  7. kilgoretrout

    kilgoretrout

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    That's not entirely correct. In linux, the boot partition must be within the bios limit. That allows linux to load the kernel. Once the kernel is loaded, linux kisses the bios, and its hard drive size limitations, goodbye. If your not booting from the drive, it's no problem at all. Linux should see the entire drive. Windows is much more bound to the bios limits than linux.
     
  8. jackmanplus

    jackmanplus

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    already know this

    i already know this and on my dell i got cheated out of 15GB, doesn't seem like a lot until you check price on 20GB hard drives. also, since lots of people are viewing this thread, please help me with problem: Drives and Storage > DLA from sonic wont stop :) thanks
     
  9. sids

    sids

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    So here we are exactly at my little problem.
    For some days I'm trying to set up a
    - Linux Server with MandrakeLinux 10.1.
    an old
    -P1 200Mhz Box, with a "Giga-Byte" GA- 586tx Mainboard.
    I've bougt a new Samsung 80 GB HD, but had to jumper it to 32 GB, otherwise the BIOS won't recognize it. I've already flashed the BIOS, but without success in the 32GB issue.
    I tried an old Altec MUX-MuFu IDE-Controller I found, but it blocks the system from booting ( Same IRQ 14 than the onboard IDE-Controller). It has a dozent jumper and no setupguide.

    when I changed BIOS Setting that the HD wasn't detected by the bios, i was able to format the HD with 74 GB, but system doesn't boot from HD anymore.

    Next Idea was an old 2GB Disk as BootHD and 80GB as "DATA- Drive". is that possible? How?

    Is it possible to freeup the "missing" 42 GB? Partitioning of the HD is as follows:
    / (root / Boot) 5GB
    Swap 0,5GB
    /home 27 GB

    Any hints, Ideas and discussion is welcome. (Well, this realy a no budget project!)
    thanks,
    sids
     
    Last edited: Jan 24, 2005
  10. glc

    glc Forum Administrator Staff Member

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    Please start a new thread, sids. This sticky thread is an information thread, not one for discussing individual issues. Thank you!

    Hint: Get a plug and play controller card that's compatible with your Linux distro.
     
  11. PSYCHOPIXIE

    PSYCHOPIXIE

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    Re

    Until I ran Everest software today I always thought my HD was only 13.9gb in size as reported by the pc. However Everest tells me it is 20GB. Can anyone explain that? I run xp home on a 3 year old pentium 3 compaq with 400 odd mb of ram. I use a FAT 32 system.
     
  12. glc

    glc Forum Administrator Staff Member

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    The rest of your drive is taken up by the Compaq restore partition. If you open Disk Management, you will be able to see it.
     
  13. austin1

    austin1

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    lol i just wanted 2 say ur a computer EXPERT hehe i know who to ask when i have a queshion
     
  14. TheMajor

    TheMajor

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    XP also supports FAT32 partitions up to 2TB afaik. You can't create anything larger than 32GB with XP, though.
     
  15. glc

    glc Forum Administrator Staff Member

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    Windows 95 has an absolute 32gb drive size limit, regardless of file system. 95 original and 95A are FAT16 only, 95B and C are FAT32 capable.

    Windows 98 has a 137gb drive size limitation. The 2tb is the theoretical limit of FAT32, not real world. Without a patched Fdisk, 98 has issues with drives and partitions larger than 64gb, the display is all wrong and you have to use drive percentages to set up partitions, not actual sizes.

    Windows 2000 needs SP4 and EnableLargeLBA to go over 137gb, FAT32 or NTFS, XP needs SP1. I believe 2000 can create a FAT32 partition larger than 32gb, I know XP cannot.
     
  16. Dazzer

    Dazzer

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    250Gb HDD with 137Gb max problem

    I have the following drive:

    Seagate 250Gb Serial-ATA 7200rpm with 8Mb Buffer

    When I use Seagate's DiscWizard it only sees 137Gb, but the BIOS sees 250Gb ok.

    GLC suggested "EnableLargeLBA" needs to be switched on. In the BIOS it has Large/LBA auto or disabled. This is set to "auto". I have an Asus P5P800 Motherboard, bought a week ago.

    I notice the postings on the limit in Win2000 and Win98, but I have Service Pack 4 with the Win2000 OS I am using, I think. I am just reinstalling it. [DiscWizard sees 250Gb's now - so clearly SP4 wasn't installe, sorry]

    I did find a IAA utility - but this isn't supported by the 865PE chipset for my MB. So I'm worried the full 250Gb may have problems.

    Even Intel though don't make clear whether the P4 3GHz 530 is an 865PE. It's all very confusing.

    Dazzer
     
    Last edited: Jul 2, 2005
  17. ric449

    ric449

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    Did you format/partition the drive with Windows 2000 before installing the service pack? If so, then theres your problem. Right click my computer, then click manage. Navigate to disk management, and see what it says for your hard drive. If it says unallocated or unpartitioned space (I forget what exactly it says) then you have found the problem.
     
  18. glc

    glc Forum Administrator Staff Member

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  19. E-1337

    E-1337

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    I'm curious. I have the problem you described above with the 127 gb limit. I bought a new Western Digital SATA 300gb drive, with the new Asus A8N SLI Delux mobo. It has the onboard SATA, so I plugged it in, formatted it, and now when I look at the size in windows, it says 127 gb instead of 300. How do I fix this? Flash the Bios? I have drivers for the SATA controller, but those don't help. I think I might need to do this "FDisk" thing, but I don't know what it entails. Could you help?
     
  20. Cricket

    Cricket Shiro Usagi

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    Are you running WinXP? You need SP1 or higher to go past 132GB.
    It depends on the motherboard you're using but if it's a newer one you shouldn't have to.
    Again, if you're using WinXP you don't want to use FDISK...that was strickly for Win9x (Win95, Win98 and WinME).
    Next time you have a question or problem it's best to start your own thread and include more information about your computer...system specs, operating system, background programs, etc...

    :) Cricket
     

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