Concurrent disk accesses slow in Windows XP - Microsoft Windows

This is a discussion on Concurrent disk accesses slow in Windows XP - Microsoft Windows ; Hi, I have noticed very slow I/O performance in Windows XP while performing certain tasks, and I have been able to write a small test which reliably demonstrates the problem. I'd like to explain this problem and ask if anyone ...

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Thread: Concurrent disk accesses slow in Windows XP

  1. Concurrent disk accesses slow in Windows XP

    Hi,
    I have noticed very slow I/O performance in Windows XP while
    performing certain tasks, and I have been able to write a small test
    which reliably demonstrates the problem. I'd like to explain this
    problem and ask if anyone knows a workaround or set of tweaks to
    improve the situation.

    I create two large files (each too large to fit in memory, so they are
    not entirely cached), and attempt to read them back. When I read the
    files from beginning to end, one after the other, I get certain
    performance (around 35 MiB/s). When I change to reading each file in
    the same way, but read both files concurrently using threads, the
    performance drops to something miserable (around 1-2 MiB/s).

    While running the latter test I can hear my hard disk thrash heavily,
    it is clearly seeking backwards and forwards reading very little after
    each seek. The same test under Linux (same hardware) results in the
    parallel reads running only slightly slower than the sequential
    (around 32 MiB/s total throughput), and the disk is clearly seeking
    much less frequently. The same test on Mac OS X (different hardware)
    has the same characteristic as Linux.

    I have noticed this being a problem for real tasks. If I run any I/O
    intensive operation in the background while attempting any moderate I/
    O in the foreground the performance is unbearable.

    My setup is Windows XP SP2 with a bog standard SATA disk and 2GiB of
    RAM..

    Does anyone know of any settings or tweaks I can apply to mitigate
    this problem?


  2. Re: Concurrent disk accesses slow in Windows XP

    Pauldoo wrote:
    > Hi,
    > I have noticed very slow I/O performance in Windows XP while
    > performing certain tasks, and I have been able to write a small test
    > which reliably demonstrates the problem. I'd like to explain this
    > problem and ask if anyone knows a workaround or set of tweaks to
    > improve the situation.
    >
    > I create two large files (each too large to fit in memory, so they are
    > not entirely cached), and attempt to read them back. When I read the
    > files from beginning to end, one after the other, I get certain
    > performance (around 35 MiB/s). When I change to reading each file in
    > the same way, but read both files concurrently using threads, the
    > performance drops to something miserable (around 1-2 MiB/s).


    > Does anyone know of any settings or tweaks I can apply to mitigate
    > this problem?


    Well I suppose youi've done a defrag with something that seriously
    defragments?



  3. Re: Concurrent disk accesses slow in Windows XP

    On May 16, 10:07 pm, "John of Aix" wrote:
    > Pauldoo wrote:
    > > Hi,
    > > I have noticed very slow I/O performance in Windows XP while
    > > performing certain tasks, and I have been able to write a small test
    > > which reliably demonstrates the problem. I'd like to explain this
    > > problem and ask if anyone knows a workaround or set of tweaks to
    > > improve the situation.

    >
    > > I create two large files (each too large to fit in memory, so they are
    > > not entirely cached), and attempt to read them back. When I read the
    > > files from beginning to end, one after the other, I get certain
    > > performance (around 35 MiB/s). When I change to reading each file in
    > > the same way, but read both files concurrently using threads, the
    > > performance drops to something miserable (around 1-2 MiB/s).
    > > Does anyone know of any settings or tweaks I can apply to mitigate
    > > this problem?

    >
    > Well I suppose youi've done a defrag with something that seriously
    > defragments?


    Yes. The files were only slightly fragmented after first creation,
    and making sure they were fully defragged made no difference.


  4. Re: Concurrent disk accesses slow in Windows XP



    Pauldoo wrote:

    > On May 16, 10:07 pm, "John of Aix" wrote:
    >
    >>Pauldoo wrote:
    >>
    >>>Hi,
    >>>I have noticed very slow I/O performance in Windows XP while
    >>>performing certain tasks, and I have been able to write a small test
    >>>which reliably demonstrates the problem. I'd like to explain this
    >>>problem and ask if anyone knows a workaround or set of tweaks to
    >>>improve the situation.

    >>
    >>>I create two large files (each too large to fit in memory, so they are
    >>>not entirely cached), and attempt to read them back. When I read the
    >>>files from beginning to end, one after the other, I get certain
    >>>performance (around 35 MiB/s). When I change to reading each file in
    >>>the same way, but read both files concurrently using threads, the
    >>>performance drops to something miserable (around 1-2 MiB/s).
    >>>Does anyone know of any settings or tweaks I can apply to mitigate
    >>>this problem?

    >>
    >>Well I suppose youi've done a defrag with something that seriously
    >>defragments?

    >
    >
    > Yes. The files were only slightly fragmented after first creation,
    > and making sure they were fully defragged made no difference.


    Providing your drive isn't running in PIO mode (check the IDE in Device
    manager). If you force the the hard drive to chase all over the platter
    to retrieve the the data, data transfer will drop to rock bottom. You
    could increase memory, use a faster harddrive, or stop setting up
    conditions to ask the system to do someting it is not capable of doing.


  5. Re: Concurrent disk accesses slow in Windows XP

    On May 17, 3:12 pm, Bob I wrote:
    > Pauldoo wrote:
    > > On May 16, 10:07 pm, "John of Aix" wrote:

    >
    > >>Pauldoo wrote:

    >
    > >>>Hi,
    > >>>I have noticed very slow I/O performance in Windows XP while
    > >>>performing certain tasks, and I have been able to write a small test
    > >>>which reliably demonstrates the problem. I'd like to explain this
    > >>>problem and ask if anyone knows a workaround or set of tweaks to
    > >>>improve the situation.

    >
    > >>>I create two large files (each too large to fit in memory, so they are
    > >>>not entirely cached), and attempt to read them back. When I read the
    > >>>files from beginning to end, one after the other, I get certain
    > >>>performance (around 35 MiB/s). When I change to reading each file in
    > >>>the same way, but read both files concurrently using threads, the
    > >>>performance drops to something miserable (around 1-2 MiB/s).
    > >>>Does anyone know of any settings or tweaks I can apply to mitigate
    > >>>this problem?

    >
    > >>Well I suppose youi've done a defrag with something that seriously
    > >>defragments?

    >
    > > Yes. The files were only slightly fragmented after first creation,
    > > and making sure they were fully defragged made no difference.

    >
    > Providing your drive isn't running in PIO mode (check the IDE in Device
    > manager). If you force the the hard drive to chase all over the platter
    > to retrieve the the data, data transfer will drop to rock bottom. You
    > could increase memory, use a faster harddrive, or stop setting up
    > conditions to ask the system to do someting it is not capable of doing.


    I don't have direct control over the requests sent to disk. The OS
    does.

    When reading two files in parallel from different threads I'd expect
    the OS not thrash the disk. I'd expect it to compensate for the large
    seek times of the harddisk by simply requesting more data between each
    seek (just as Linux and Mac OS X do). This is not a problem in my
    application, it's a problem with the braindead OS.


    Is anyone familiar with any settings or tweaks I can apply to Windows
    XP to make it behave more sensibly? I've noticed that Microsoft have
    fixed these problems in Vista, and I wonder if the fixes are available
    to XP through settings tweaks...



  6. Re: Concurrent disk accesses slow in Windows XP

    On May 15, 5:45 pm, Pauldoo wrote:
    > Hi,
    > I have noticed veryslowI/Operformance inWindowsXPwhile
    > performing certain tasks, and I have been able to write a small test
    > which reliably demonstrates the problem. I'd like to explain this
    > problem and ask if anyone knows a workaround or set of tweaks to
    > improve the situation.
    >
    > I create two large files (each too large to fit in memory, so they are
    > not entirely cached), and attempt to read them back. When I read the
    > files from beginning to end, one after the other, I get certain
    > performance (around 35 MiB/s). When I change to reading each file in
    > the same way, but read both files concurrently using threads, the
    > performance drops to something miserable (around 1-2 MiB/s).
    >
    > While running the latter test I can hear my hard disk thrash heavily,
    > it is clearly seeking backwards and forwards reading very little after
    > each seek. The same test under Linux (same hardware) results in the
    > parallel reads running only slightly slower than the sequential
    > (around 32 MiB/s totalthroughput), and the disk is clearly seeking
    > much less frequently. The same test on Mac OS X (different hardware)
    > has the same characteristic as Linux.
    >
    > I have noticed this being a problem for real tasks. If I run anyI/O
    > intensive operation in the background while attempting any moderateI/Oin the foreground the performance is unbearable.
    >
    > My setup isWindowsXPSP2 with a bog standard SATA disk and 2GiB of
    > RAM..
    >
    > Does anyone know of any settings or tweaks I can apply to mitigate
    > this problem?


    Damn, I see the samething on my thinkpad x41 and older T30. it must be
    linked to some service or driver but i don't know which one. In fact,
    it runs perfect when it's setup, but after several weeks or months,
    suddenly it goes very slow, takes 5 minutes to go to hibernation.

    Last time I noticed it seems links to Nokia connectivity driver.


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