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    SubjectRe: single bit errors on files stored on USB-HDDs via USB2/usb_storage
    DervishD wrote:
    > Hi Matthias :)
    >
    > * Matthias Schniedermeyer <ms@citd.de> dixit:
    >
    >>My averate file size is about 1GB with files from about 400MB to
    >>5000MB I estimate the average error-rate at about one damaged file in
    >>about 10GB of data.
    >>
    >>I'm not sure and haven't checked if the files are wrongly written or
    >>"only" wrongly read back as i delete the defective files and copy them
    >>again.
    >>
    >>Today i copied a few files back and checked them against the stored MD5
    >>sums and 5 files of 86 (each about 700 MB) had errors. So i copied the 5
    >>files again. 4 of the files were OK after that and coping the last file
    >>the third time also resulted in the correct MD5.
    >
    >
    > I had more or less the same issue a week or two ago. I performed
    > lots of tests and only by replacing the USB2.0 PCI card, the USB cable
    > and the power supply of the usb-hdd adapter got the problem solved.
    >
    > I'm not sure if the problem is really gone, but the system works now
    > reliably. I don't know if sooner or later I'll get the issue again,
    > because I didn't really identify a culprit: looks like the
    > card+adapter+cable combination was just "ugly", and errors from the
    > adapter were not reported correctly.

    The 38 HDDs are in 38 enclosures, so each has it's own power supply. I
    have used different cables and i replaced the USB-Controller once.

    So it can't be a single faulty component. Except when the computer
    itself would be the culprit.

    >>NEVER did i see any messages in syslog regarding erros or an aborting
    >>program due to errors passed down from the kernel or something like
    >>that.
    >
    > The same here! Looks like USB-HDD adapters don't report any errors
    > to the kernel :?????
    >
    > The best advice I can give you, from my limited experience with the
    > problem, is: replace the cable. This minimizes the chance of corrupted
    > data getting into the adapter. If that doesn't solve the problem, try
    > removing any unconnected cable that is plugged into the USB card.
    > Believe it or not, a long but unconnected cable (put there just to be
    > able to plug my USB card-reader without having to look for the cable in
    > a drawer) was causing errors *even in a Kingston USB key that worked
    > flawlessly otherwise*!!!

    Hmmm. That's the only thing that i currently may be doing wrong.
    I have a 1,5 Meter and a 4,5 Meter cable connected to the USB-Controller
    and i only use of them depending on where the HDD is placed in my room,
    the other one is dangling unconnected.

    Then i will unconnect the short cable and use the long cable exclusivly
    and see if it gets better(tm).

    > If you have any other question, feel free to drop me a note. I'm
    > sorry I cannot give a much more technical or scientific answer, but
    > unfortunately I have none :((

    Thank you anyway.





    Bis denn

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