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    SubjectRe: True fsync() in Linux (on IDE)
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    Date
    On Fri, 2004-03-19 at 14:26, Peter Zaitsev wrote:
    > 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.
    >
    It is indeed.

    > 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
    >
    All of the above is correct.

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

    For the suse patch, yes. If it triggers a commit, you get a cache
    flush.

    >
    > 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)

    These are all difficult issues. I wish I had easier answers for you,
    hopefully we can get it all nailed down in 2.6 for starters.

    -chris


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