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I want to format some large (500GB to 1 TB) external hard drives so that they are universally read/write accessible from any modern operating system - Win, Linux, BSD, Mac, ...
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  1. #1
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    UDF for external USB drives?


    I want to format some large (500GB to 1 TB) external hard drives so that they are universally read/write accessible from any modern operating system - Win, Linux, BSD, Mac, whatever. And I want to be able to do this natively from these OSs without loaded any installable drivers.

    Content and file sizes will be mixed - anything from text files of several KB to multi-GB movie files. I am not concerned about file ownership, permissions, etc.

    Seems to me that UDF (Universal Disk Format, IEC 13346/ECMA-167) is what I want to use. Although it's commonly used on DVDs and CDs, occasionally on Compact Flash and thumb drives, I see hardly any mention of it for hard drives beyond the mere fact that it's possible.

    I know it's possible, at least on small drives. I stuck an old 10GB drive in an external USB case, plugged it into a Win7 machine, formatted it UDF (from the CLI,"Format D: /FS:UDF"), copied some PDF files to it, read them back, plugged it into my laptop running SL6 (RHEL6) read the PDFs, added more files to it, took it back to the Win7 machine, read them.

    So far, so good.

    But what about larger drives, like 500GB or 1 TB ? Any reason to not use UDF on those ? Any reason to not use UDF at all ? Is there anything better ?

    What worries me is, if UDF is as good and universal as it seems, why isn't everybody using it for hard disks ?

    Life has taught me to ask that very question. Too many times, I've gone against the herd only to eventually find out the hard way that there was a very good reason nobody else did it my way.

  2. #2
    Linux Guru Rubberman's Avatar
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    UDF was designed for read-mostly media. While you might be able to do what you want with it, there are a number of caveats, and implementation issues. This Wikipedia article covers some of those issues. In any case I'm sure a lot of us will be interested in your experiences with this.

    Universal Disk Format - Wikipedia, the free encyclopedia
    Sometimes, real fast is almost as good as real time.
    Just remember, Semper Gumbi - always be flexible!

  3. #3
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    Well, it SEEMED like a good idea at the time. Worked great until I plugged it into a WinXP box.

    I tested it on a 500GB Seagate SATA drive in an external LaCie USB enclosure, formatted UDF in Win7.

    - Win7 read/wrote to it just fine.
    - Linux (SL6/RHEL6) read/wrote to it just fine.

    I could do either one or both all day long. I copied countless files of various sizes back and forth between linux and win7. However...

    - I plugged it into a WinXP(SP3) box. It reads just fine. I try to write a file to it, XP says it's 'read only' and won't write. Not only that, but after having attempted a write from XP, I can no longer write to it from Win7 which now thinks I have zero space left on it. It's as if XP thought it was a CD-R and 'finalized' it.

    For me, at the moment, until I learn more about file systems, it's a showstopper.

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  5. #4
    Linux Guru Rubberman's Avatar
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    Well, Windows XP/Vista/Win7, Linux, and OSX all can read/write NTFS formatted volumes, and that can handle very large file systems quite efficiently. Have you tried that? FWIW, the Linux driver for that is ntfs-3g. You can get that from the epel repository, so assuming you have epel installed, you can simply issue the command: yum install ntfs-3g
    Sometimes, real fast is almost as good as real time.
    Just remember, Semper Gumbi - always be flexible!

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