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    SubjectRe: disk statistics issue in 2.6.27
    On Mon, 2008-10-20 at 19:12 +0200, Jens Axboe wrote:
    > On Sun, Oct 19 2008, Miquel van Smoorenburg wrote:
    > > I just upgraded one of our servers in the nntp cluster to -
    > > most of the others are running 2.6.26.something.
    > >
    > > I noticed that the "iostat -k -x 2" output does't make any sense.
    > > The number of reads/sec and number of writes/sec are about what I
    > > would expect, and so are the other fields, but rkB/sec and wkB/sec
    > > are completely off-scale: gigabytes read/written per second.
    > Weird, I cannot reproduce this at all, iostat works fine for me in .26,
    > .27 and current -git as well. So it's just a plain SCSI drive from
    > linux, no software raid or dm?

    It's a 3-disk hardware RAID5 array, Adaptec 2005S, dpt_i2o driver.

    > Are the reported values in iostat any sort of multiple of the real
    > throughtput, or is is just insanely large?

    It looks like it's a multiple, but it appears to vary between 128 and
    512, and is different for reads and writes, so I do not know what to
    make of it.

    I tried to reproduce it on different systems - on another box with a
    2010S controller I'm seeing the same thing. But on a different box with
    SATA drives I cannot reproduce the problem.

    Thanks for looking at this. I guess I'll have to start putting debug
    statements in block/gendisk.c to find out what's wrong. I might not have
    time for it until after next week though, but I won't give up :)


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