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    SubjectSMP 2.1.131: SCSI performance extremely poor vs. IDE
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    I've received a report of extremely poor SCSI performance in the late
    2.1.x kernels and verified this under 2.1.131.

    I tested this by untarring the mozilla source onto the local hard
    drive, syncing, and rm -rf ing it.

    The mozilla source is 91.6 megabytes untarred.

    The results are astounding:

    [ben@gilgamesh:/tmp]% time rm -rf mozilla 4:15PM
    rm -rf mozilla 0.13s user 0.93s system 18% cpu 5.581 total

    [ben@beowulf:/tmp]% time rm -rf mozilla 4:15PM
    rm -rf mozilla 0.17s user 1.51s system 98% cpu 1.712 total

    This is, frankly, terrible. Since when is IDE three times faster than
    ultra-wide SCSI?

    The first computer, gilgamesh, is a SCSI-based Pentium II/333 system;
    using the aic7xxx driver version 5.1.4/3.2.4 for its Adaptec AHA-294X
    Ultra Wide SCSI controller to control an IBM DDRS-39130W ultra-wide
    drive.

    The second computer, beowulf, is an IDE-based dual Pentium Pro/200
    system, PIIX3 IDE controller, ST39140A IDE drive.

    Both are compiled with SMP = 1.

    One would think that the SCSI Pentium II/333 system, even though it's
    single-processor, would have decent disk performance! Is there
    something I'm missing?

    So as to not spam the list with the .configs of the two machines,
    I've put them up on the Web for your perusal:

    http://csl.cse.ucsc.edu/~ben/ide-config
    http://csl.cse.ucsc.edu/~ben/scsi-config

    What would cause this kind of performance loss?

    For an interesting comparison, here's the same test on an UltraSPARC:

    bash$ time rm -rf mozilla/

    real 1.1
    user 0.2
    sys 0.7

    Ben

    --
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