Exact size of a pen drive

By chessonly
May 8, 2009
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  1. SImple question : whats the exact size of a 1gb pendrive ?

    940 MB ?

    990MB
    1024 MB ?
    Here's what right > properties shows me
    [​IMG]

    Is this correct ? The reason I ask is because I think I may have messed up my pen-drive on linux
  2. kimsland

    kimsland Ex-TechSpotter Posts: 18,353

    That looks right to me :grinthumb

    As for the exact size, well part of the space is used by the filesystem (Fat32) and I think there's some other memory amount used as well. Anyway, you never get exactly the stated amount on any drive (in your case 1024 Meg)
  3. chessonly

    chessonly Newcomer, in training Topic Starter Posts: 65

    ok so its 1 giga bytes = 947 MB

    not 1024 MB

    Thanks
  4. account73

    account73 Newcomer, in training Posts: 65

    No, 1 gigabyte = 1024mb
    Your's shows 947mb because of the stuff kimsland said.
  5. SNGX1275

    SNGX1275 TS Forces Special Posts: 12,264   +215

    Its actually 1GB=1,000,000,000bytes according to the manufacturer. So when you start dividing that by 1024 to get KB you get 976,562.5. Then divide that by 1024 to get MB and you come up with 953.67, which is pretty close to what you see. There may be some FS overhead in there.

    Mine actually shows a bit higher. But the apparent discrepancy you see is almost certainly because of the difference in what manufacturers consider a GB and what computer users consider a GB (1000 vs 1024).

    Attached Files:

  6. account73

    account73 Newcomer, in training Posts: 65

    Seems odd to me how a computer user and a manufacturer would consider 1 GB as different size in mb.
    Thats like having the police and every day road users seeing 70mph as different. For the police 70 mph is 100kmh and for road users 70 mph is 120kmh
    ( Yes i know those kmh numbers are wrong for the speed in mph, i just made them up =)
    Am i getting confused or am i right in thinking different manufactures are seeing 1gb as different sizes when it's converted to mb? sorry for going away from the orginal topic question aswell, this just interesting me.
  7. SNGX1275

    SNGX1275 TS Forces Special Posts: 12,264   +215

    I don't know why you wouldn't believe me, but whatever. Its exactly like I said it was.

    From Seagate Barracuda data sheet "1 One gigabyte, or GB, equals one billion bytes and one terabyte, or TB, equals one trillion bytes when referring to hard drive capacity."

    From Western Digital Specifications for Caviar Black HDs "As used for storage capacity, one megabyte (MB) = one million bytes, one gigabyte (GB) = one billion bytes, and one terabyte (TB) = one trillion bytes. Total accessible capacity varies depending on operating environment. As used for buffer or cache, one megabyte (MB) = 1,048,576 bytes. As used for transfer rate or interface, megabyte per second (MB/s) = one million bytes per second, megabit per second (Mb/s) = one million bits per second, and gigabit per second (Gb/s) = one billion bits per second."

    From Hitachi Deskstar data sheet: " One GB is equal to one billion bytes and one TB equals 1,000GB (one trillion bytes) when referring to hard drive capacity. Accessible capacity
    may be less."


    From Samsung Spinpoint hard drives page: "1MB = 1,000,000bytes / 1GB = 1,000,000,000 bytes.
    Actual accessible capacity may vary from advertised capacity due to formatting and
    partitioning of the hard drive, as well as due to your computer's operating system"


    From Fujitsu enterprise hard drives page: "1 One gigabyte (GB) = one billion bytes; accessible capacity will be less and actual capacity depends on the operating environment and formatting.
    One megabyte (MB) = 1,000,000 bytes; One gigabyte (GB) = 1,000 megabytes; Gigabit (Gb) = 1,000 megabits; RPM = Revolutions Per Minute
    2 A small portion of buffer memory is used for drive firmware control
    "
  8. account73

    account73 Newcomer, in training Posts: 65

    SNGX1275, it's not that i didnt beleive you :) i've never doubted what you said.
    I was just getting a little confused and found it odd how different places would see it as different sizes.
    It's good to learn new stuff. I like to learn new stuff thats why i ask, so thanks for all the info ! =)
  9. xehqter

    xehqter Newcomer, in training Posts: 85

    Short Answer: What Kimsland Said

    Long Answer: Unlike hard drives which are generally larger and have the size artificially capped (ie: 80GB platter capped as 40GB) by the manufacture to whatever size they want. NAND memory is sold in fixed capacities ie: 8Gbit (1GByte, 1024MB), so you start with 1024MB, take away space for the controllers firmware, spare blocks, translation tables, and whatever proprietary modules / data structures are unique to that controller or manufacture and that gives you the raw space logical space. Then you throw the filesystem on and that adds extra overhead. All this means that one manufactures 1GB flash drive may be bigger or smaller than the others depending on how its configured. The only time you’ll see 1024MB in a 1GB flash drive is if it’s a fake (the controller has been programmed to lie about its size) or if they stuck a 2GB flash chip in the drive and capped it at 1024MB.

    In the latter I’ve seen that twice, on cheap Chinese thumb drives given out at conventions, the memory chips were from the reject pile (failed tests, to many bad blocks) and the extra 1GB area was used as spare space for remapping bad blocks.
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