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    SubjectRe: Understanding I/O behaviour
    On 5 Jul, 16:50, Martin Knoblauch <> wrote:
    > Hi,
    > for a customer we are operating a rackful of HP/DL380/G4 boxes that
    > have given us some problems with system responsiveness under [I/O
    > triggered] system load.

    IIRC, the locking in the CCISS driver was pretty heavy until later in
    the 2.6 series (2.6.16?) kernels; I don't think they were backported
    to the 1000 or so patches that comprise RH EL 4 kernels.

    With write performance being really poor on the Smartarray controllers
    without the battery-backed write cache, and with less-good locking,
    performance can really suck.

    On a total quiescent hp DL380 G2 (dual PIII, 1.13GHz Tualatin 512KB
    L2$) running RH EL 5 (2.6.18) with a 32MB SmartArray 5i controller
    with 6x36GB 10K RPM SCSI disks and all latest firmware:

    # dd if=/dev/cciss/c0d0p2 of=/dev/zero bs=1024k count=1000
    509+1 records in
    509+1 records out
    534643200 bytes (535 MB) copied, 11.6336 seconds, 46.0 MB/s

    # dd if=/dev/zero of=/dev/cciss/c0d0p2 bs=1024k count=100
    100+0 records in
    100+0 records out
    104857600 bytes (105 MB) copied, 22.3091 seconds, 4.7 MB/s

    Oh dear! There are internal performance problems with this controller.
    The SmartArray 5i in the newer DL380 G3 (dual P4 2.8GHz, 512KB L2$) is
    perhaps twice the read performance (PCI-X helps some) but still sucks.

    I'd get the BBWC in or install another controller.

    Daniel J Blueman
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