Messages in this thread | | | Subject | Re: weird throughput on write to SATA disk | From | kenneth johansson <> | Date | Mon, 13 Oct 2008 23:22:36 +0200 |
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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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