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    SubjectRe: Integration of SCST in the mainstream Linux kernel
    On Feb 5, 2008 6:10 PM, Erez Zilber <> wrote:
    > One may claim that STGT should have lower performance than SCST because
    > its data path is from userspace. However, your results show that for
    > non-IB transports, they both show the same numbers. Furthermore, with IB
    > there shouldn't be any additional difference between the 2 targets
    > because data transfer from userspace is as efficient as data transfer
    > from kernel space.
    > The only explanation that I see is that fine tuning for iSCSI & iSER is
    > required. As was already mentioned in this thread, with SDR you can get
    > ~900 MB/sec with iSER (on STGT).

    My most recent measurements also show that one can get 900 MB/s with
    STGT + iSER on an SDR IB network, but only for very large block sizes
    (>= 100 MB). A quote from Linus Torvalds is relevant here (February 5,

    Block transfer sizes over about 64kB are totally irrelevant for
    99% of all people.

    Please read my e-mail (posted earlier today) with a comparison for 4
    KB - 64 KB block transfer sizes between SCST and STGT.

    Bart Van Assche.

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