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    SubjectRe: True fsync() in Linux (on IDE)
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    On Fri, 2004-03-19 at 05:52, Chris Mason wrote:


    > I am listening to Peter, Jens and I have spent a significant amount of
    > time on this code. We can go back and spend many more hours testing and
    > debugging the 2.4 changes, or we can go forward with a very nice
    > solution in 2.6.
    >
    > I'm planning on going forward with 2.6

    Chris, Hans

    It is great to hear this is going to be fixed in 2.6, however it is
    quite a pity we have a real mess with this in 2.4 series.

    Resuming what I've heard so far it looks like it depends on:

    - If it is fsync/O_SYNC or O_DIRECT (which user would expect to have
    the same effect in this respect.
    - It depends on kernel version. Some vendors have some fixes, while
    others do not have them.
    - It depends on hardware - if it has write cache on or off
    - It depends on type of write (if it changes mata data or not)
    - Finally it depends on file system and even journal mount options

    Just curious does at least Asynchronous IO have the same behavior as
    standard IO ?


    All of these makes it extremely hard to explain what do users need in
    order to get durability for their changes, while preserving performance.

    Furthermore as it was broken for years I expect we'll have people which
    developed things with fast fsync() in mind, who would start screaming
    once we have real fsync()

    (see my mail about Apple actually disabling cache flush on fsync() due
    to this reason)




    --
    Peter Zaitsev, Senior Support Engineer
    MySQL AB, www.mysql.com

    Meet the MySQL Team at User Conference 2004! (April 14-16, Orlando,FL)
    http://www.mysql.com/uc2004/

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