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  • Lum
    Lum Posts: 6,460 Forumite
    Part of the Furniture 1,000 Posts Photogenic Combo Breaker
    Handsome90 wrote: »
    If I need to get around the 4GB limit of FAT32, I reformat my drive to exFAT.

    Only supported on Snow Leopard or higher for Macs.

    XP needs this update

    Poor support on Linux and on other USB devices (though admittedly the latter is also true for NTFS)

    exFAT also has a few design issues that make it a lot harder than FAT or NTFS if it gets damaged and you need to recover.

    It's a good solution if your OS meets the above requirements and you aren't using it for backup or long term storage, however, and so may work for the OP, so a good call subject to those caveats.
  • andy2004
    andy2004 Posts: 1,309 Forumite
    To test you flash drive isnt fake, theres a freeware app it will write onto it so make sure theres no data on it, then at the end it will tell you, delete the files it created and use. no installation, small, main program is 409kb
    used it to test ALL my flash drives, as it also tells you about data speed
    name of program is h2testw 1.4.
    Download link http://www.softpedia.com/get/System/System-Miscellaneous/H2testw.shtml
    when you first run it i suggest you click ENGLISH as it starts up in Deutsch
    from the readme file
    H2testw -- by Harald Bögeholz / c't Magazin für Computertechnik
    Data integrity test for USB sticks and other media
    Version 1.4, Copyright (C) 2008 Heise Zeitschriften Verlag GmbH & Co. KG
    ========================================================================

    H2testw was developed to test USB sticks for various kinds of errors.
    It can also be used for any other storage media like memory cards,
    internal and external hard drives and even network volumes.

    The executable file H2testw.exe needs no installation and can be
    directly run. It was developed for Windows XP and Vista. It should
    also work under Windows 2000 but was only tested on XP and Vista.
    Windows 9x/ME is not supported. You can use the older command line
    program H2test under these operating systems.

    The function of H2testw is quite simple: It fills the chosen target
    directory with test data and then reads it back and verifies it.

    H2testw does not overwrite or erase any existing data. It doesn't
    do any low-level tricks so administrator privileges are not required.
    If your hardware is working properly H2testw will not harm any
    existing data.

    BUT: _If_ the hardware is defective then H2testw is designed to find
    that defect and might as a side effect damage existing files.
    Therefore: IF YOU SUSPECT A USB STICK OR OTHER STORAGE MEDIA TO BE
    DEFECTIVE, EMPTY IT AND TEST IT COMPLETELY WITH H2TESTW. Only empty
    media can be fully tested with H2testw. In order to be able to
    reproduce the results we recommend to format the media (quick format
    will do) and then test it.

    H2testw writes files of up to 1 GByte to the chosen destination and
    names them 1.h2w, 2.h2w, 3.h2w and so on. If the target directory
    alread contains such a set of files H2testw will offer to verify them.
    If there are any other files named *.h2w it will refuse to work. In
    that case please erase all files *.h2w and hit the Refresh button.

    After it is done the software leaves its test files on the medium.
    You can erase them if you like or verify them again -- if it's a USB
    stick for instance with another PC.

    The check box "endless verify" does just that: It puts the verify
    routine in an endless loop that stops only if an error is found. This
    is meant to be used as a long-time test to find sporadic data transfer
    errors.

    A remark on the estimated time remaining: For intact flash memory the
    estimate should be pretty exact since it has a constant data rate.
    With defective media we have seen massive drops in the transfer rate
    resulting in the estimate increasing instead of decreasing. Hard
    drives are slower on the inner tracks than on the outer tracks so when
    testing a hard drive the estimate is never precise.

    If you have any questions or suggestions for H2testw please send an
    email to Harald Bögeholz <hwb@heise.de> (in German or English).


    What to do in case of errors

    If H2benchw finds errors while verifying the data it means that the
    media has not returned all data exactly as it was written. It is
    likely that the media is defective, but there are other possible
    causes for data corruption. In case of error you should therefore
    repeat the test and

    * Format the media immediately before testing

    * Don't use USB extension cords

    * If testing USB or FireWire devices, try a different port (sometimes
    USB ports at the back of the PC are better than those at the front)

    * For exteral drives try another cable if possible


    Error messages

    When the verifying process detects any errors it outputs some
    statistics differentiating the various error types:

    * sectors that have been overwritten by others due to addressing
    errors (see above)

    * sectors that have been altered only slightly (less than 8 differing
    bits per sector)

    * completely corrupted sectors.

    In the case of overwritten sectors H2testw tries to find out how much
    real memory exists in the overwritten area and outputs that amount as
    "aliased memory" (no guarantee here).

    Finally it outputs the offset of the first error with regard to the
    total amount of test data along with the expected and found value at
    that offset.

    Hint: You can copy&paste the error message, for instance to send it in
    an email.


    Typical errors

    The test data of H2testw is made up so as to be able to discern
    certain typical errors. There are three types:

    * Addressing errors: When writing a sector its contents are not
    written to the correct address but overwrite another sector. We have
    seen this error on certain manipulated USB sticks. It also happens
    if you use a hard drive larger than 128 GByte on a machine whose
    BIOS or OS doesn't know about 48-bit addressing. In this case all
    addresses are taken modulo 128 GByte. When crossing the 128 GByte
    boundary you overwrite data at the beginning of the drive.

    * Data is not saved at all. We have encountered this with defective
    USB sticks. Instead of the data written to it a sector returns only
    ones or zeroes when reading it. This is typical when accessing
    nonexisting memory.

    * Only few bits of data are changed. That might happen if the
    connection between the PC and the storage media is faulty.


    Technical details about the test data

    H2testw writes data in chunks of 1 megabyte. So even if you choose to
    completely fill the media you will end up with up to 1 megabyte of
    free space. Although technically not correct H2testw uses the
    Windows convention that 1 MByte equals 1024 KByte or 1,048,576 Byte.
    In order to avoid problems with the 4 GByte limitation of the FAT file
    system, H2testw begins a new data file after each gigabyte (1024
    MByte).

    Inside a data file each 512-byte sector begins with a 64-bit word (8
    byte) containing the offset with regard to the whole data set. It is
    stored in little-endian format, least significant byte first.

    So the file 1.h2w begins with

    00 00 00 00 00 00 00 00,

    the next sector with

    00 02 00 00 00 00 00 00,

    the next with

    00 04 00 00 00 00 00 00

    and so on. The file 2.h2w begins with

    00 00 00 40 00 00 00 00

    (offset 1 GByte = 0x40000000).

    The rest of each sector is filled with a pseudo random number
    sequence using the offset word as a seed.
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