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Thread: write cache (win/Storage)

  1. write cache (win/Storage)

    According to technet the option to "enable write cache" in the policies
    window (w2k3) always has an impact on the setting of the underlying
    storage, no matter if it's a single dumb sata disk or a high-end
    storage-subsystem with integrated RAID-controller.
    I do understand that this setting always implies windows OS caching.
    Or is it a driver's setting?
    All tests I did confirmed that behaviour regarding IBM DS4700 storage.
    When you tick the option the IBM storage manager shows an altered
    setting as well. So obviously SCSI commands trigger the setting on the DS.
    If hard disk caching is disabled, performance drops to 15% (SATA, duh).
    Now I want to DISABLE windows OS caching completely, but leave caching
    on for the underlying storage.
    Would that sound reasonable (and possible)?
    Thanks.

  2. Re: write cache (win/Storage)

    Previously Ingo wrote:
    > According to technet the option to "enable write cache" in the policies
    > window (w2k3) always has an impact on the setting of the underlying
    > storage, no matter if it's a single dumb sata disk or a high-end
    > storage-subsystem with integrated RAID-controller.
    > I do understand that this setting always implies windows OS caching.
    > Or is it a driver's setting?
    > All tests I did confirmed that behaviour regarding IBM DS4700 storage.
    > When you tick the option the IBM storage manager shows an altered
    > setting as well. So obviously SCSI commands trigger the setting on the DS.
    > If hard disk caching is disabled, performance drops to 15% (SATA, duh).
    > Now I want to DISABLE windows OS caching completely, but leave caching
    > on for the underlying storage.
    > Would that sound reasonable (and possible)?


    Not really. UNless you do not trust your OS. For Windows, this
    may still be a reasonable idea, as the technology is not up
    to the standards of other OSes.

    As to whether it is possible, you can only disable OS buffering.
    I thinkt his wirks by marking the device as "removable".
    You will still get application buffering. What you do not want to
    disable is caching. Caching only influences read access, by
    delivering already read stuff from memory (MS here again
    confuses the terminologuy: There is no write caching. It is
    either read caching or write buffering).

    Arno

  3. Re: write cache (win/Storage)

    Arno Wagner schrieb:
    > Previously Ingo wrote:
    >> According to technet the option to "enable write cache" in the policies
    >> window (w2k3) always has an impact on the setting of the underlying
    >> storage, no matter if it's a single dumb sata disk or a high-end
    >> storage-subsystem with integrated RAID-controller.
    >> I do understand that this setting always implies windows OS caching.
    >> Or is it a driver's setting?
    >> All tests I did confirmed that behaviour regarding IBM DS4700 storage.
    >> When you tick the option the IBM storage manager shows an altered
    >> setting as well. So obviously SCSI commands trigger the setting on the DS.
    >> If hard disk caching is disabled, performance drops to 15% (SATA, duh).
    >> Now I want to DISABLE windows OS caching completely, but leave caching
    >> on for the underlying storage.
    >> Would that sound reasonable (and possible)?

    >
    > Not really. UNless you do not trust your OS. For Windows, this
    > may still be a reasonable idea, as the technology is not up
    > to the standards of other OSes.
    >
    > As to whether it is possible, you can only disable OS buffering.
    > I thinkt his wirks by marking the device as "removable".
    > You will still get application buffering. What you do not want to
    > disable is caching. Caching only influences read access, by
    > delivering already read stuff from memory (MS here again
    > confuses the terminologuy: There is no write caching. It is
    > either read caching or write buffering).
    >
    > Arno


    Thanks for the answer (and the side blow to Win, of course The reason
    I want to do this is having two Win that share one LUN in a SAN. One
    machine dies, the other seamlessly takes over (write sessions, it's a
    backup app). The app requires having the mentioned Win setting turned
    off (or using your term write buffering). Alas, as described above, that
    also disables caching on the storage controller for that specific LUN.
    I'm not sure every storage vendor does this. I think HDS Thunder leaves
    its caching setting on.
    I want to be sure that write operations (acknowledged "back" from OS to
    the app) have found their way to the storage (leaving out windows
    buffering) in case of desaster. I cannot set "remov. device", it's
    greyed out. Oh yeah, there's a app driver (similar to Win cluster
    service for quorum) that disallows all settings for the LUN on the
    passive node. Maybe that's what "trusting your OS" is all about and the
    reason the backup sw vendor also requires that setting to be off.
    Am I having it right? Do I lose data when my active machine dies?
    Thanks.

  4. Re: write cache (win/Storage)

    Previously Ingo wrote:
    > Arno Wagner schrieb:
    >> Previously Ingo wrote:
    >>> According to technet the option to "enable write cache" in the policies
    >>> window (w2k3) always has an impact on the setting of the underlying
    >>> storage, no matter if it's a single dumb sata disk or a high-end
    >>> storage-subsystem with integrated RAID-controller.
    >>> I do understand that this setting always implies windows OS caching.
    >>> Or is it a driver's setting?
    >>> All tests I did confirmed that behaviour regarding IBM DS4700 storage.
    >>> When you tick the option the IBM storage manager shows an altered
    >>> setting as well. So obviously SCSI commands trigger the setting on the DS.
    >>> If hard disk caching is disabled, performance drops to 15% (SATA, duh).
    >>> Now I want to DISABLE windows OS caching completely, but leave caching
    >>> on for the underlying storage.
    >>> Would that sound reasonable (and possible)?

    >>
    >> Not really. UNless you do not trust your OS. For Windows, this
    >> may still be a reasonable idea, as the technology is not up
    >> to the standards of other OSes.
    >>
    >> As to whether it is possible, you can only disable OS buffering.
    >> I thinkt his wirks by marking the device as "removable".
    >> You will still get application buffering. What you do not want to
    >> disable is caching. Caching only influences read access, by
    >> delivering already read stuff from memory (MS here again
    >> confuses the terminologuy: There is no write caching. It is
    >> either read caching or write buffering).
    >>
    >> Arno


    > Thanks for the answer (and the side blow to Win, of course The reason
    > I want to do this is having two Win that share one LUN in a SAN. One
    > machine dies, the other seamlessly takes over (write sessions, it's a
    > backup app). The app requires having the mentioned Win setting turned
    > off (or using your term write buffering). Alas, as described above, that
    > also disables caching on the storage controller for that specific LUN.
    > I'm not sure every storage vendor does this. I think HDS Thunder leaves
    > its caching setting on.
    > I want to be sure that write operations (acknowledged "back" from OS to
    > the app) have found their way to the storage (leaving out windows
    > buffering) in case of desaster. I cannot set "remov. device", it's
    > greyed out. Oh yeah, there's a app driver (similar to Win cluster
    > service for quorum) that disallows all settings for the LUN on the
    > passive node. Maybe that's what "trusting your OS" is all about and the
    > reason the backup sw vendor also requires that setting to be off.
    > Am I having it right? Do I lose data when my active machine dies?
    > Thanks.


    Ok, so you wan a device accessed directly from multiple installations
    of Windows. Sorry, but for that you need an OS that can actually
    handle this. Windows cannot. Linux, incidentially, also cannot
    really, as far as I know. This suggests that your approach is wrong.

    What could be possible under Linux is to multi-host the SCSI and
    to only load the SCSI drive on one machine. When that one fails,
    you can switch it off (using a remote power swicth) and then load
    the SCSI drive on the second box, reset the bus and maybe access the
    disk. This strikes me as overly complex though.

    Thisrd approach: Use Linux and mirror the drive remotely to the
    second machine. This means you need two instances of your storage.
    The mirroring schould be possible wth the righ filesystem, maybe GFS.

    This needs more research, but having one storage device under
    the control of two OSes is not normally possible and done.

    Arno

  5. Re: write cache (win/Storage)

    Previously Arno Wagner wrote:
    [...]
    > Ok, so you wan a device accessed directly from multiple installations
    > of Windows. Sorry, but for that you need an OS that can actually
    > handle this. Windows cannot. Linux, incidentially, also cannot
    > really, as far as I know. This suggests that your approach is wrong.


    > What could be possible under Linux is to multi-host the SCSI and
    > to only load the SCSI drive on one machine. When that one fails,
    > you can switch it off (using a remote power swicth) and then load
    > the SCSI drive on the second box, reset the bus and maybe access the
    > disk. This strikes me as overly complex though.


    > Thisrd approach: Use Linux and mirror the drive remotely to the
    > second machine. This means you need two instances of your storage.
    > The mirroring schould be possible wth the righ filesystem, maybe GFS.


    > This needs more research, but having one storage device under
    > the control of two OSes is not normally possible and done.


    P.S.: Here is the main problem: Both OSes need a constistent
    picture of the device at any time. Since one does not know
    when the other wtote somewhere, all on disk data and metadata
    would have to be read at each time it was used, no caching at all.
    And the device would need to be locked against accesses by the
    other one at times. While theoretically possible, you would get likely
    <1% of the performance you get with ordinary accessess. Therefore
    you do this either with one machine controlling the storage and
    use remote access, or you replicate not only the machine, but
    also the storage and mirror the data.

    Arno

  6. Re: write cache (win/Storage)

    Arno Wagner schrieb:
    > Previously Ingo wrote:
    >> Arno Wagner schrieb:
    >>> Previously Ingo wrote:
    >>>> According to technet the option to "enable write cache" in the policies
    >>>> window (w2k3) always has an impact on the setting of the underlying
    >>>> storage, no matter if it's a single dumb sata disk or a high-end
    >>>> storage-subsystem with integrated RAID-controller.
    >>>> I do understand that this setting always implies windows OS caching.
    >>>> Or is it a driver's setting?
    >>>> All tests I did confirmed that behaviour regarding IBM DS4700 storage.
    >>>> When you tick the option the IBM storage manager shows an altered
    >>>> setting as well. So obviously SCSI commands trigger the setting on the DS.
    >>>> If hard disk caching is disabled, performance drops to 15% (SATA, duh).
    >>>> Now I want to DISABLE windows OS caching completely, but leave caching
    >>>> on for the underlying storage.
    >>>> Would that sound reasonable (and possible)?
    >>> Not really. UNless you do not trust your OS. For Windows, this
    >>> may still be a reasonable idea, as the technology is not up
    >>> to the standards of other OSes.
    >>>
    >>> As to whether it is possible, you can only disable OS buffering.
    >>> I thinkt his wirks by marking the device as "removable".
    >>> You will still get application buffering. What you do not want to
    >>> disable is caching. Caching only influences read access, by
    >>> delivering already read stuff from memory (MS here again
    >>> confuses the terminologuy: There is no write caching. It is
    >>> either read caching or write buffering).
    >>>
    >>> Arno

    >
    >> Thanks for the answer (and the side blow to Win, of course The reason
    >> I want to do this is having two Win that share one LUN in a SAN. One
    >> machine dies, the other seamlessly takes over (write sessions, it's a
    >> backup app). The app requires having the mentioned Win setting turned
    >> off (or using your term write buffering). Alas, as described above, that
    >> also disables caching on the storage controller for that specific LUN.
    >> I'm not sure every storage vendor does this. I think HDS Thunder leaves
    >> its caching setting on.
    >> I want to be sure that write operations (acknowledged "back" from OS to
    >> the app) have found their way to the storage (leaving out windows
    >> buffering) in case of desaster. I cannot set "remov. device", it's
    >> greyed out. Oh yeah, there's a app driver (similar to Win cluster
    >> service for quorum) that disallows all settings for the LUN on the
    >> passive node. Maybe that's what "trusting your OS" is all about and the
    >> reason the backup sw vendor also requires that setting to be off.
    >> Am I having it right? Do I lose data when my active machine dies?
    >> Thanks.

    >
    > Ok, so you wan a device accessed directly from multiple installations
    > of Windows. Sorry, but for that you need an OS that can actually
    > handle this. Windows cannot. Linux, incidentially, also cannot
    > really, as far as I know. This suggests that your approach is wrong.
    >
    > What could be possible under Linux is to multi-host the SCSI and
    > to only load the SCSI drive on one machine. When that one fails,
    > you can switch it off (using a remote power swicth) and then load
    > the SCSI drive on the second box, reset the bus and maybe access the
    > disk. This strikes me as overly complex though.
    >
    > Thisrd approach: Use Linux and mirror the drive remotely to the
    > second machine. This means you need two instances of your storage.
    > The mirroring schould be possible wth the righ filesystem, maybe GFS.
    >
    > This needs more research, but having one storage device under
    > the control of two OSes is not normally possible and done.
    >
    > Arno


    Hello Arno,
    you got me wrong :-) Of course the storage is only configured in a SAN
    to be accessible by both OSs (once again see MSCS quorum disk, Shared
    Storage). Going down to Miliseconds you are right. Of course it's EITHER
    one OS (machine) OR the other accessing the LUN. You're apt to lose data
    when both do it REALLY SIMULTANEOUSLY (signatures, inodes etc.) As long
    as both systems are alive the Failover is handled fine. There are
    cluster-aware Apps (one of which is my Backup app). So now I've come
    back to my OP again. What happens when the active OS dies?
    Obviously I haven't made myself clear here.
    Have a nice weekend

  7. Re: write cache (win/Storage)

    Ingo schrieb:
    > Arno Wagner schrieb:
    >> Previously Ingo wrote:
    >>> Arno Wagner schrieb:
    >>>> Previously Ingo wrote:
    >>>>> According to technet the option to "enable write cache" in the
    >>>>> policies window (w2k3) always has an impact on the setting of the
    >>>>> underlying storage, no matter if it's a single dumb sata disk or a
    >>>>> high-end storage-subsystem with integrated RAID-controller.
    >>>>> I do understand that this setting always implies windows OS caching.
    >>>>> Or is it a driver's setting?
    >>>>> All tests I did confirmed that behaviour regarding IBM DS4700
    >>>>> storage. When you tick the option the IBM storage manager shows an
    >>>>> altered setting as well. So obviously SCSI commands trigger the
    >>>>> setting on the DS.
    >>>>> If hard disk caching is disabled, performance drops to 15% (SATA,
    >>>>> duh).
    >>>>> Now I want to DISABLE windows OS caching completely, but leave
    >>>>> caching on for the underlying storage.
    >>>>> Would that sound reasonable (and possible)?
    >>>> Not really. UNless you do not trust your OS. For Windows, this
    >>>> may still be a reasonable idea, as the technology is not up
    >>>> to the standards of other OSes.
    >>>>
    >>>> As to whether it is possible, you can only disable OS buffering.
    >>>> I thinkt his wirks by marking the device as "removable".
    >>>> You will still get application buffering. What you do not want to
    >>>> disable is caching. Caching only influences read access, by
    >>>> delivering already read stuff from memory (MS here again confuses
    >>>> the terminologuy: There is no write caching. It is
    >>>> either read caching or write buffering).
    >>>>
    >>>> Arno

    >>
    >>> Thanks for the answer (and the side blow to Win, of course The
    >>> reason I want to do this is having two Win that share one LUN in a
    >>> SAN. One machine dies, the other seamlessly takes over (write
    >>> sessions, it's a backup app). The app requires having the mentioned
    >>> Win setting turned off (or using your term write buffering). Alas, as
    >>> described above, that also disables caching on the storage controller
    >>> for that specific LUN. I'm not sure every storage vendor does this. I
    >>> think HDS Thunder leaves its caching setting on.
    >>> I want to be sure that write operations (acknowledged "back" from OS
    >>> to the app) have found their way to the storage (leaving out windows
    >>> buffering) in case of desaster. I cannot set "remov. device", it's
    >>> greyed out. Oh yeah, there's a app driver (similar to Win cluster
    >>> service for quorum) that disallows all settings for the LUN on the
    >>> passive node. Maybe that's what "trusting your OS" is all about and
    >>> the reason the backup sw vendor also requires that setting to be off.
    >>> Am I having it right? Do I lose data when my active machine dies?
    >>> Thanks.

    >>
    >> Ok, so you wan a device accessed directly from multiple installations
    >> of Windows. Sorry, but for that you need an OS that can actually
    >> handle this. Windows cannot. Linux, incidentially, also cannot
    >> really, as far as I know. This suggests that your approach is wrong.
    >>
    >> What could be possible under Linux is to multi-host the SCSI and
    >> to only load the SCSI drive on one machine. When that one fails,
    >> you can switch it off (using a remote power swicth) and then load
    >> the SCSI drive on the second box, reset the bus and maybe access the
    >> disk. This strikes me as overly complex though.
    >> Thisrd approach: Use Linux and mirror the drive remotely to the
    >> second machine. This means you need two instances of your storage.
    >> The mirroring schould be possible wth the righ filesystem, maybe GFS.
    >>
    >> This needs more research, but having one storage device under
    >> the control of two OSes is not normally possible and done.
    >>
    >> Arno

    >
    > Hello Arno,
    > you got me wrong :-) Of course the storage is only configured in a SAN
    > to be accessible by both OSs (once again see MSCS quorum disk, Shared
    > Storage). Going down to Miliseconds you are right. Of course it's EITHER
    > one OS (machine) OR the other accessing the LUN. You're apt to lose data
    > when both do it REALLY SIMULTANEOUSLY (signatures, inodes etc.) As long
    > as both systems are alive the Failover is handled fine. There are
    > cluster-aware Apps (one of which is my Backup app). So now I've come
    > back to my OP again. What happens when the active OS dies?
    > Obviously I haven't made myself clear here.
    > Have a nice weekend

    p.s. I think I know the misunderstanding now... the application is not
    constantly "failing over" between the two OSs!!! Of course that would be
    performance=0. No no, one machine writes for weeks, then dies. That's
    the situation.

  8. Re: write cache (win/Storage)

    Previously Ingo wrote:
    > Arno Wagner schrieb:
    >> Previously Ingo wrote:
    >>> Arno Wagner schrieb:
    >>>> Previously Ingo wrote:
    >>>>> According to technet the option to "enable write cache" in the policies
    >>>>> window (w2k3) always has an impact on the setting of the underlying
    >>>>> storage, no matter if it's a single dumb sata disk or a high-end
    >>>>> storage-subsystem with integrated RAID-controller.
    >>>>> I do understand that this setting always implies windows OS caching.
    >>>>> Or is it a driver's setting?
    >>>>> All tests I did confirmed that behaviour regarding IBM DS4700 storage.
    >>>>> When you tick the option the IBM storage manager shows an altered
    >>>>> setting as well. So obviously SCSI commands trigger the setting on the DS.
    >>>>> If hard disk caching is disabled, performance drops to 15% (SATA, duh).
    >>>>> Now I want to DISABLE windows OS caching completely, but leave caching
    >>>>> on for the underlying storage.
    >>>>> Would that sound reasonable (and possible)?
    >>>> Not really. UNless you do not trust your OS. For Windows, this
    >>>> may still be a reasonable idea, as the technology is not up
    >>>> to the standards of other OSes.
    >>>>
    >>>> As to whether it is possible, you can only disable OS buffering.
    >>>> I thinkt his wirks by marking the device as "removable".
    >>>> You will still get application buffering. What you do not want to
    >>>> disable is caching. Caching only influences read access, by
    >>>> delivering already read stuff from memory (MS here again
    >>>> confuses the terminologuy: There is no write caching. It is
    >>>> either read caching or write buffering).
    >>>>
    >>>> Arno

    >>
    >>> Thanks for the answer (and the side blow to Win, of course The reason
    >>> I want to do this is having two Win that share one LUN in a SAN. One
    >>> machine dies, the other seamlessly takes over (write sessions, it's a
    >>> backup app). The app requires having the mentioned Win setting turned
    >>> off (or using your term write buffering). Alas, as described above, that
    >>> also disables caching on the storage controller for that specific LUN.
    >>> I'm not sure every storage vendor does this. I think HDS Thunder leaves
    >>> its caching setting on.
    >>> I want to be sure that write operations (acknowledged "back" from OS to
    >>> the app) have found their way to the storage (leaving out windows
    >>> buffering) in case of desaster. I cannot set "remov. device", it's
    >>> greyed out. Oh yeah, there's a app driver (similar to Win cluster
    >>> service for quorum) that disallows all settings for the LUN on the
    >>> passive node. Maybe that's what "trusting your OS" is all about and the
    >>> reason the backup sw vendor also requires that setting to be off.
    >>> Am I having it right? Do I lose data when my active machine dies?
    >>> Thanks.

    >>
    >> Ok, so you wan a device accessed directly from multiple installations
    >> of Windows. Sorry, but for that you need an OS that can actually
    >> handle this. Windows cannot. Linux, incidentially, also cannot
    >> really, as far as I know. This suggests that your approach is wrong.
    >>
    >> What could be possible under Linux is to multi-host the SCSI and
    >> to only load the SCSI drive on one machine. When that one fails,
    >> you can switch it off (using a remote power swicth) and then load
    >> the SCSI drive on the second box, reset the bus and maybe access the
    >> disk. This strikes me as overly complex though.
    >>
    >> Thisrd approach: Use Linux and mirror the drive remotely to the
    >> second machine. This means you need two instances of your storage.
    >> The mirroring schould be possible wth the righ filesystem, maybe GFS.
    >>
    >> This needs more research, but having one storage device under
    >> the control of two OSes is not normally possible and done.
    >>
    >> Arno


    > Hello Arno,
    > you got me wrong :-) Of course the storage is only configured in a SAN
    > to be accessible by both OSs (once again see MSCS quorum disk, Shared
    > Storage). Going down to Miliseconds you are right. Of course it's EITHER
    > one OS (machine) OR the other accessing the LUN. You're apt to lose data
    > when both do it REALLY SIMULTANEOUSLY (signatures, inodes etc.) As long
    > as both systems are alive the Failover is handled fine. There are
    > cluster-aware Apps (one of which is my Backup app). So now I've come
    > back to my OP again. What happens when the active OS dies?
    > Obviously I haven't made myself clear here.
    > Have a nice weekend



    So your question is what happens to the dat on disk when the OS dies
    while there still is information in the buffer not yet flushed to
    disk? Well, that depends on the filesystem and the application.
    Conceptually this is not really different from the machine dying while
    that application is in the process of writing and there is no
    write-buffer. Turning off the buffer does not really help that
    much. It just reduces the risk a bit and reduces the amount of data
    ''in flight'' (i.e. where the app thinks it has written, but it is not
    on disk). This only matters if there is outside communication that
    then could be told the wrong thing. Unless your application does
    single sector writes with disc-buffer flushes after them, you
    allways need to be prepared for aborted writes, combined
    with a system crash.

    Arno

  9. Re: write cache (win/Storage)

    Arno Wagner wrote in news:6eb2veF6a8smU1@mid.individual.net
    > Previously Ingo wrote:
    > > According to technet the option to "enable write cache" in the policies
    > > window (w2k3) always has an impact on the setting of the underlying
    > > storage, no matter if it's a single dumb sata disk or a high-end
    > > storage-subsystem with integrated RAID-controller.
    > > I do understand that this setting always implies windows OS caching.
    > > Or is it a driver's setting?
    > > All tests I did confirmed that behaviour regarding IBM DS4700 storage.
    > > When you tick the option the IBM storage manager shows an altered
    > > setting as well. So obviously SCSI commands trigger the setting on the DS.
    > > If hard disk caching is disabled, performance drops to 15% (SATA, duh).
    > > Now I want to DISABLE windows OS caching completely, but leave caching
    > > on for the underlying storage.
    > > Would that sound reasonable (and possible)?

    >
    > Not really. UNless you do not trust your OS. For Windows, this
    > may still be a reasonable idea, as the technology is not up
    > to the standards of other OSes.
    >
    > As to whether it is possible, you can only disable OS buffering.
    > I thinkt his wirks by marking the device as "removable".
    > You will still get application buffering. What you do not want to
    > disable is caching. Caching only influences read access, by
    > delivering already read stuff from memory (MS here again
    > confuses the terminologuy: There is no write caching.


    > It is either read caching or write buffering).


    Utter nonsense, as always from the babblebot

    >
    > Arno


  10. Re: write cache (win/Storage)

    Squeeze schrieb:
    > Arno Wagner wrote in news:6eb2veF6a8smU1@mid.individual.net
    >> Previously Ingo wrote:
    >>> According to technet the option to "enable write cache" in the policies
    >>> window (w2k3) always has an impact on the setting of the underlying
    >>> storage, no matter if it's a single dumb sata disk or a high-end
    >>> storage-subsystem with integrated RAID-controller.
    >>> I do understand that this setting always implies windows OS caching.
    >>> Or is it a driver's setting?
    >>> All tests I did confirmed that behaviour regarding IBM DS4700 storage.
    >>> When you tick the option the IBM storage manager shows an altered
    >>> setting as well. So obviously SCSI commands trigger the setting on the DS.
    >>> If hard disk caching is disabled, performance drops to 15% (SATA, duh).
    >>> Now I want to DISABLE windows OS caching completely, but leave caching
    >>> on for the underlying storage.
    >>> Would that sound reasonable (and possible)?

    >> Not really. UNless you do not trust your OS. For Windows, this
    >> may still be a reasonable idea, as the technology is not up
    >> to the standards of other OSes.
    >>
    >> As to whether it is possible, you can only disable OS buffering.
    >> I thinkt his wirks by marking the device as "removable".
    >> You will still get application buffering. What you do not want to
    >> disable is caching. Caching only influences read access, by
    >> delivering already read stuff from memory (MS here again
    >> confuses the terminologuy: There is no write caching.

    >
    >> It is either read caching or write buffering).

    >
    > Utter nonsense, as always from the babblebot
    >
    >> Arno

    well Squeeze... since I'm really stuck here, you might want to share
    what you think?!
    Problem in a nutshell again:
    - cluster aware app requires "enable write caching on disk" to be
    disabled in Win 2k3 OS policy pane of disk mgmt (my guess is that is
    because power failure of SERVER)
    - doing that disables caching in storage subsystem as well
    (these being SATA disks, performance drops)
    - i don't want that
    - so question: is there a way to disable OS caching (server failure no
    problem) without disabling underlying storage caching mechanism? If not,
    wtf. Option "optimze for quick removal" is of course not available
    Thanks
    Ingo

  11. Re: write cache (win/Storage)

    Previously Ingo wrote:
    > Squeeze schrieb:
    >> Arno Wagner wrote in news:6eb2veF6a8smU1@mid.individual.net
    >>> Previously Ingo wrote:
    >>>> According to technet the option to "enable write cache" in the policies
    >>>> window (w2k3) always has an impact on the setting of the underlying
    >>>> storage, no matter if it's a single dumb sata disk or a high-end
    >>>> storage-subsystem with integrated RAID-controller.
    >>>> I do understand that this setting always implies windows OS caching.
    >>>> Or is it a driver's setting?
    >>>> All tests I did confirmed that behaviour regarding IBM DS4700 storage.
    >>>> When you tick the option the IBM storage manager shows an altered
    >>>> setting as well. So obviously SCSI commands trigger the setting on the DS.
    >>>> If hard disk caching is disabled, performance drops to 15% (SATA, duh).
    >>>> Now I want to DISABLE windows OS caching completely, but leave caching
    >>>> on for the underlying storage.
    >>>> Would that sound reasonable (and possible)?
    >>> Not really. UNless you do not trust your OS. For Windows, this
    >>> may still be a reasonable idea, as the technology is not up
    >>> to the standards of other OSes.
    >>>
    >>> As to whether it is possible, you can only disable OS buffering.
    >>> I thinkt his wirks by marking the device as "removable".
    >>> You will still get application buffering. What you do not want to
    >>> disable is caching. Caching only influences read access, by
    >>> delivering already read stuff from memory (MS here again
    >>> confuses the terminologuy: There is no write caching.

    >>
    >>> It is either read caching or write buffering).

    >>
    >> Utter nonsense, as always from the babblebot
    >>
    >>> Arno

    > well Squeeze... since I'm really stuck here, you might want to share
    > what you think?!
    > Problem in a nutshell again:
    > - cluster aware app requires "enable write caching on disk" to be
    > disabled in Win 2k3 OS policy pane of disk mgmt (my guess is that is
    > because power failure of SERVER)
    > - doing that disables caching in storage subsystem as well
    > (these being SATA disks, performance drops)
    > - i don't want that
    > - so question: is there a way to disable OS caching (server failure no
    > problem) without disabling underlying storage caching mechanism? If not,
    > wtf. Option "optimze for quick removal" is of course not available
    > Thanks
    > Ingo


    Don't expect anything from that person.

    Arno

  12. Re: write cache (win/Storage)

    Ingo wrote in news:g6c7hd$km7$1@newsreader2.netcologne.de
    > Squeeze schrieb:
    > > Arno Wagner wrote in news:6eb2veF6a8smU1@mid.individual.net
    > > > Previously Ingo wrote:
    > > > > According to technet the option to "enable write cache" in the policies
    > > > > window (w2k3) always has an impact on the setting of the underlying
    > > > > storage, no matter if it's a single dumb sata disk or a high-end
    > > > > storage-subsystem with integrated RAID-controller.
    > > > > I do understand that this setting always implies windows OS caching.
    > > > > Or is it a driver's setting?
    > > > > All tests I did confirmed that behaviour regarding IBM DS4700 storage.
    > > > > When you tick the option the IBM storage manager shows an altered
    > > > > setting as well. So obviously SCSI commands trigger the setting on the DS.
    > > > > If hard disk caching is disabled, performance drops to 15% (SATA, duh).
    > > > > Now I want to DISABLE windows OS caching completely, but leave caching
    > > > > on for the underlying storage.
    > > > > Would that sound reasonable (and possible)?
    > > > Not really. UNless you do not trust your OS. For Windows, this
    > > > may still be a reasonable idea, as the technology is not up
    > > > to the standards of other OSes.
    > > >
    > > > As to whether it is possible, you can only disable OS buffering.
    > > > I thinkt his wirks by marking the device as "removable".
    > > > You will still get application buffering. What you do not want to
    > > > disable is caching. Caching only influences read access, by
    > > > delivering already read stuff from memory (MS here again
    > > > confuses the terminologuy: There is no write caching.

    > >
    > > > It is either read caching or write buffering).

    > >
    > > Utter nonsense, as always from the babblebot.
    > >
    > > > Arno


    > well Squeeze... since I'm really stuck here, you might want to share
    > what you think?!


    What makes you think that if I knew a solution I wouldn't share it with
    you first time but I would second time?

    I think that you should go to the storage newsgroup, comp.arch.storage .

    > Problem in a nutshell again:
    > - cluster aware app requires "enable write caching on disk" to be
    > disabled in Win 2k3 OS policy pane of disk mgmt (my guess is that is
    > because power failure of SERVER)
    > - doing that disables caching in storage subsystem as well
    > (these being SATA disks, performance drops)


    > - i don't want that


    Tough luck. That's what it takes to make sure that data read from the drive
    is actually on the platters and not in some cache or buffer, drive or otherwise.

    > - so question: is there a way to disable OS caching (server failure no
    > problem) without disabling underlying storage caching mechanism? If not,
    > wtf. Option "optimze for quick removal" is of course not available
    > Thanks
    > Ingo


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