Re: Apparent strange disk behaviour in 6.0

From: Poul-Henning Kamp (phk_at_phk.freebsd.dk)
Date: 07/30/05

  • Next message: Peter Grehan: "re: Rockridge extension not enabled when / is cd9660, boot fails" 
    To: Julian Elischer <julian@elischer.org>
Date: Sat, 30 Jul 2005 12:33:55 +0200

    In message <42EB5687.2070400@elischer.org>, Julian Elischer writes:
    >Poul-Henning Kamp wrote:
    >> In message <42E88135.30603@elischer.org>, Julian Elischer writes:
    >>
    >> Please use gstat and look at the service times instead of the
    >> busy percentage.
    >
    >The snapshot below is typical when doing tar from one drive to another..
    >(tar c -C /disk1 f- .|tar x -C /disk2 -f - )
    >
    >dT: 1.052 flag_I 1000000us sizeof 240 i -1
    > L(q) ops/s r/s kBps ms/r w/s kBps ms/w d/s kBps ms/d %busy Name
    > 0 405 405 1057 0.2 0 0 0.0 0 0 0.0 9.8 | ad0
    > 0 405 405 1057 0.3 0 0 0.0 0 0 0.0 11.0 | ad0s2
    > 0 866 3 46 0.4 863 8459 0.7 0 0 0.0 63.8 | da0
    > 25 866 3 46 0.5 863 8459 0.8 0 0 0.0 66.1 | da0s1
    > 0 405 405 1057 0.3 0 0 0.0 0 0 0.0 12.1 | ad0s2f
    > 195 866 3 46 0.5 863 8459 0.8 0 0 0.0 68.1 | da0s1d
    >
    >even though the process should be disk limitted neither of the disks is anywhere
    >near 100%.

    This looks like an awful lot of small files since you write 8 times as much data
    as you read ?

    Since the write service time (ms/w) is low, I pressume you have
    some hefty disk hardware (with cache ?)

    Presumably you're using softupdates ?

    I wouldn't be surprised if you were limited by system time rather than disk in
    this scenario ? 

    -- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.
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  • Next message: Peter Grehan: "re: Rockridge extension not enabled when / is cd9660, boot fails"

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