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    SubjectRe: weird throughput on write to SATA disk
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    On Mon, 2008-10-13 at 14:07 -0700, Grant Grundler wrote:
    > On Mon, Oct 13, 2008 at 12:19 PM, kenneth johansson <ken@kenjo.org> wrote:
    > > When writing data to /dev/sdb (that is the whole disk and no filesystem)
    > > it starts out ok around 100MB/sec but soon end up doing considerably
    > > worse. For prolonged times lasting several minutes it hovers in the
    > > 20-30MB/sec.
    >
    > Is the application using "O_DIRECT"?

    no just open then write no fancy stuff

    > If not, could be issue with how VM writeback is (not) working.

    the access pattern is the simplest possible. Is there any knobs I could
    try to adjust.

    > Can you reproduce this using fio or even "dd"?
    > (See git://git.kernel.dk/fio)

    dd is having the same effect.




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