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    SubjectRe: queue_nr_requests needs to be selective
    Jeff V. Merkey [jmerkey@vger.timpanogas.org] wrote:
    >
    > ..snip..
    >
    > What is really needed here is to allow queue_nr_requests to be
    > configurable on a per adapter/device basis for these high end
    > raid cards like 3Ware since in a RAID 0 configuration, 8 drives
    > are in essence a terabyte (1.3 terrabytes in our configuration)
    > and each adapter is showing up as a 1.3 TB device. 64/128
    > requests are simply not enough to get the full spectrum of
    > performance atainable with these cards.
    >
    Not having direct experience on this card it appears that increasing the
    queue_nr_requests number will not allow you to have more ios in flight.

    Unless I am reading the driver wrong you will be limited to
    TW_MAX_CMDS_PER_LUN (15). This value is used by scsi_build_commandblocks
    to allocate scsi commands for your scsi_device. This driver does not provide
    a select_queue_depths function which allows for increase to the default
    template value.

    Could it be that the experimentation of increasing this number has
    allowed for better merging.

    -Mike
    --
    Michael Anderson
    andmike@us.ibm.com

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