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    SubjectRe: SATA Performance with Intel ICH6
    Date
    Am Freitag, 24. November 2006 15:30 schrieben Sie:
    > On Fri, 24 Nov 2006 15:10:11 +0100
    > "Martin A. Fink" <fink@mpe.mpg.de> wrote:
    >
    > > Well this seems to be independend from the file system. I tried to write
    > > directly to the raw device, but nevertheless the cpu time was 20% (sys
    time).
    >
    > sys time is not neccessarily CPU time.
    >
    > > This is an interessting point. The specification say that I can handle
    around
    > > 120 to 150 MB/s each of the 4 S-ATA ports. With ICH6 the S-ATA ports seem
    to
    >
    > At once ?
    >
    > > be directly connected to the Southbridge, and the Southbridge is directly
    > > connected to Northbridge via PCI Express. So it should be possible to get
    150
    > > MB/s from north to south and from there in packages of 55 MB/s to the
    > > disks ?!
    >
    > Ask the vendor.
    >
    > > <6>scsi1 : ata_piix
    > > <5> Vendor: ATA Model: WDC WD740GD-75FL Rev: 21.0
    > > <5> Type: Direct-Access ANSI SCSI revision: 05
    >
    > The PIIX interface needs CPU intervention each command, so in practice
    > about every 64K or so, and the CPU gets stalled waiting for the disk
    > during the setup of each I/O. The newer kernels support AHCI which does
    > not have this overhead, but it is only present on the newest intel
    > controllers.

    Can you tell me the name of this controllers? Is it ICH7 or 8 ?
    What kernel versions?

    Thank you very much
    >
    > > and strace dd... gives among other information
    > > 6.84s 1004calls syscall: write
    > >
    > > So I spend 45s of 52s within the kernel. Why so long?
    >
    > Waiting for the disk I would imagine.
    >
    > Alan
    >
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    --
    Dipl. Physiker
    Martin Anton Fink
    Max Planck Institute for extraterrestrial Physics
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