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    SubjectSATA Performance with Intel ICH6
    Date
    Dear all,

    I found out, that writing to a SATA harddisk costs around 20% of the
    computers cpu time. I write blocks of 1MB size to a file. Write performance
    is around 51MB/s what I think is really good. My computer has an Intel ICH6
    chipset and a 3.2GHz Pentium 4 processor.
    If I understand the design of this chipset correctly, then I would have
    expected, that the CPU needs to do only few work, instead I found out, that
    writing to disk seems to be really hard work for the CPU.

    Can I do anything to optimize writing from memory to disk?

    My final aim is to get around 140MB/s of data from 3 different Gigabit
    Ethernet cards and store it on 3 harddisk drives that perform 50MB/s.
    From the SATA bus side there should be no problem. Each of the 4 SATAs on
    this ICH6 chipset are capable of 150MB/s.

    So what makes my CPU that slow? Is it a hardware problem or a problem of
    SATA driver of my operating system?

    time dd if=/dev/zero of=test.zero bs=1M count=1000
    results in

    real 0m52.561s
    user 0m0.003s
    sys 0m7.407s

    and strace dd... gives among other information
    6.84s 1004calls syscall: write

    So I spend 45s of 52s within the kernel. Why so long?


    By the way: I'm working with SuSE Linux 9.2 on a Dell Desktop PC, 1GB RAM

    Thank you for answers,

    Martin
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