Cheap Way To Share Fibre Channel Storage - Storage

This is a discussion on Cheap Way To Share Fibre Channel Storage - Storage ; I'm looking for a cheap way to have more than one computer share read-only access to fibre channel storage under Windows 2000. I'm using Compaq fibre channel arrays for the hardware, and those are fine for low-end use, but they ...

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Thread: Cheap Way To Share Fibre Channel Storage

  1. Cheap Way To Share Fibre Channel Storage

    I'm looking for a cheap way to have more than one computer share
    read-only access to fibre channel storage under Windows 2000.
    I'm using Compaq fibre channel arrays for the hardware, and those
    are fine for low-end use, but they don't have any option
    internally to give read-only access. A host is designated in
    the Compaq software as either having full access or no access.
    If multiple Windows hosts try to write to the same logical
    device, they will trash sensitive file system structures on the
    disk.

    Is there any low-priced software that would run as a service on
    Windows that would prevent any attempt to write to designated
    disks? The service would need to be fairly low level and would
    need to prevent the Windows kernel from writing to the disk.

    --
    Will
    Internet: westes at earthbroadcast.com



  2. Re: Cheap Way To Share Fibre Channel Storage


    I tried this in the past. It turns out that NTFS won't even mount a LUN
    that declares itself to be Read-Only. In the end we put an ugly hack
    into the array firmware that pretended to accept writes from the
    servers but then just threw them away. The problem with this is that it
    works too well, because the servers do some local buffering; When the
    users on the servers "wrote" new files to the read-only array it
    actually seemed as if the files were being written. Their icons
    appeared, and when they re-opened those files they contained the right
    contents - except that they were all being served up from the local
    buffer, rather than coming from the array. Needless to say, when the
    LUN was unmounted and then remounted the users were very surprised to
    see none of their newly written files.

    So you have to either find a way to do a read-only mount, or just make
    all file access go through a centralized CIFS or NFS server where you
    can do access control.



    On 2005-05-28 12:13:01 -0700, "Will" said:

    > I'm looking for a cheap way to have more than one computer share
    > read-only access to fibre channel storage under Windows 2000.
    > I'm using Compaq fibre channel arrays for the hardware, and those
    > are fine for low-end use, but they don't have any option
    > internally to give read-only access. A host is designated in
    > the Compaq software as either having full access or no access.
    > If multiple Windows hosts try to write to the same logical
    > device, they will trash sensitive file system structures on the
    > disk.
    >
    > Is there any low-priced software that would run as a service on
    > Windows that would prevent any attempt to write to designated
    > disks? The service would need to be fairly low level and would
    > need to prevent the Windows kernel from writing to the disk.




  3. Re: Cheap Way To Share Fibre Channel Storage

    wrote in message news:2005052817592516807%@news.dslextreme.com...
    >
    > I tried this in the past. It turns out that NTFS won't even mount a LUN
    > that declares itself to be Read-Only. In the end we put an ugly hack
    >

    WinNT4 did have that bug with read-only, Microsoft claims it was fixed in
    Win2K.



  4. Re: Cheap Way To Share Fibre Channel Storage

    The application is a flight simulation system that requires several
    computers to act together loading large numbers of files that provide
    terrain and texture data. So we won't have "users" trying to write files
    to these file systems. What you describe sounds perfect for our
    application.

    Which array were you using, and is the "hack" a published one?

    --
    Will
    Internet: westes AT earthbroadcast.com


    wrote in message news:2005052817592516807%@news.dslextreme.com...
    >
    > I tried this in the past. It turns out that NTFS won't even mount a LUN
    > that declares itself to be Read-Only. In the end we put an ugly hack
    > into the array firmware that pretended to accept writes from the
    > servers but then just threw them away. The problem with this is that it
    > works too well, because the servers do some local buffering; When the
    > users on the servers "wrote" new files to the read-only array it
    > actually seemed as if the files were being written. Their icons
    > appeared, and when they re-opened those files they contained the right
    > contents - except that they were all being served up from the local
    > buffer, rather than coming from the array. Needless to say, when the
    > LUN was unmounted and then remounted the users were very surprised to
    > see none of their newly written files.
    >
    > So you have to either find a way to do a read-only mount, or just make
    > all file access go through a centralized CIFS or NFS server where you
    > can do access control.




  5. Re: Cheap Way To Share Fibre Channel Storage

    > I tried this in the past. It turns out that NTFS won't even mount a LUN
    > that declares itself to be Read-Only.


    Fixed in XP and w2k3.

    --
    Maxim Shatskih, Windows DDK MVP
    StorageCraft Corporation
    maxim@storagecraft.com
    http://www.storagecraft.com



  6. Re: Cheap Way To Share Fibre Channel Storage

    On Sat, 28 May 2005 12:13:01 -0700, "Will" wrote:

    >I'm looking for a cheap way to have more than one computer share
    >read-only access to fibre channel storage under Windows 2000.


    Might not be suitable for your application, but... mount the volume on
    one server and export it as a CIFS share. The other machines can then
    access it over the LAN, and they could have full read/write access if
    you want.

    HVB

  7. Re: Cheap Way To Share Fibre Channel Storage

    Will wrote:
    > I'm looking for a cheap way to have more than one computer share
    > read-only access to fibre channel storage under Windows 2000.
    > I'm using Compaq fibre channel arrays for the hardware, and those
    > are fine for low-end use, but they don't have any option
    > internally to give read-only access. A host is designated in
    > the Compaq software as either having full access or no access.
    > If multiple Windows hosts try to write to the same logical
    > device, they will trash sensitive file system structures on the
    > disk.
    >
    > Is there any low-priced software that would run as a service on
    > Windows that would prevent any attempt to write to designated
    > disks? The service would need to be fairly low level and would
    > need to prevent the Windows kernel from writing to the disk.
    >


    Cisco MDS switches support read-only zones. I believe its a licensed
    feature. Not exactly cheap if you don't already own Cisco fibre channel
    switches, but I thought it was worth mentioning.

  8. Re: Cheap Way To Share Fibre Channel Storage

    Curious how a FC switch would have any knowledge of the file system, file
    name, the SCSI block allocation per file, so it could implement file system
    "read only" locking? Very curious....
    "Jon Metzger" wrote in message
    news:d7hmrp$5bp$1@lenny.tc.umn.edu...
    > Will wrote:
    > > I'm looking for a cheap way to have more than one computer share
    > > read-only access to fibre channel storage under Windows 2000.
    > > I'm using Compaq fibre channel arrays for the hardware, and those
    > > are fine for low-end use, but they don't have any option
    > > internally to give read-only access. A host is designated in
    > > the Compaq software as either having full access or no access.
    > > If multiple Windows hosts try to write to the same logical
    > > device, they will trash sensitive file system structures on the
    > > disk.
    > >
    > > Is there any low-priced software that would run as a service on
    > > Windows that would prevent any attempt to write to designated
    > > disks? The service would need to be fairly low level and would
    > > need to prevent the Windows kernel from writing to the disk.
    > >

    >
    > Cisco MDS switches support read-only zones. I believe its a licensed
    > feature. Not exactly cheap if you don't already own Cisco fibre channel
    > switches, but I thought it was worth mentioning.




  9. Re: Cheap Way To Share Fibre Channel Storage


    "Will" wrote in message
    news:GqqdnV_F9pR6VwXfRVn-1Q@giganews.com...
    >
    > Is there any low-priced software that would run as a service on
    > Windows that would prevent any attempt to write to designated
    > disks? The service would need to be fairly low level and would
    > need to prevent the Windows kernel from writing to the disk.


    Even if such a utility exists, it will not help you because you need all the
    systems in "share" group to be aware of writes, even if only one of them is
    allowed to write. The reason is that the read-only machines may get stale
    data from the disk because the "writer" has cached writes not yet committed
    to disk that may impact filesystem structures or file content. You could
    also get problems with writes that are partially complete when one of the
    readers tries to read.

    The only way this can be done safely is with a shared filesystem designed
    for the task. On Windows you should look at Tivoli SANergy as possible
    solution, see

    http://www-306.ibm.com/software/tivo...ducts/sanergy/


    --
    Nik Simpson



  10. Re: Cheap Way To Share Fibre Channel Storage

    No, our application is write once every two weeks, but read
    10,000 times a day. We don't need to track writes to the disk,
    and on those days when writes take place, the readers can simply
    be rebooted.

    I really do need something very very simple.

    --
    Will
    Internet: westes at earthbroadcast.com


    "Nik Simpson" wrote in message
    newsbWqe.117372$J25.6212@bignews6.bellsouth.net...
    >
    > "Will" wrote in message
    > news:GqqdnV_F9pR6VwXfRVn-1Q@giganews.com...
    > >
    > > Is there any low-priced software that would run as a service

    on
    > > Windows that would prevent any attempt to write to designated
    > > disks? The service would need to be fairly low level and

    would
    > > need to prevent the Windows kernel from writing to the disk.

    >
    > Even if such a utility exists, it will not help you because you

    need all the
    > systems in "share" group to be aware of writes, even if only

    one of them is
    > allowed to write. The reason is that the read-only machines may

    get stale
    > data from the disk because the "writer" has cached writes not

    yet committed
    > to disk that may impact filesystem structures or file content.

    You could
    > also get problems with writes that are partially complete when

    one of the
    > readers tries to read.
    >
    > The only way this can be done safely is with a shared

    filesystem designed
    > for the task. On Windows you should look at Tivoli SANergy as

    possible
    > solution, see
    >
    > http://www-306.ibm.com/software/tivo...ducts/sanergy/
    >
    >
    > --
    > Nik Simpson
    >
    >




  11. Re: Cheap Way To Share Fibre Channel Storage

    On Sun, 12 Jun 2005 11:21:05 -0700, "Will"
    wrote:

    >No, our application is write once every two weeks, but read
    >10,000 times a day. We don't need to track writes to the disk,
    >and on those days when writes take place, the readers can simply
    >be rebooted.
    >
    >I really do need something very very simple.


    I've heard there is some sort of registry setting or add-in that would
    allow you to do a Read-only NTFS mount. Can't get much simpler than
    that.


  12. Re: Cheap Way To Share Fibre Channel Storage

    Here is a URL for an article that discusses registry changes to create
    READ-ONLY removable media. I'm not sure that it is pertinent to the
    subject of this thread. A larger problem appears to be the FS mount.
    http://windowsitpro.com/windowsstora...380/44380.html


  13. Re: Cheap Way To Share Fibre Channel Storage

    > I've heard there is some sort of registry setting or add-in that would
    > allow you to do a Read-only NTFS mount. Can't get much simpler than


    XP and later can do this by default without any tuning. w2k and earlier -
    cannot without a disk filter driver.

    --
    Maxim Shatskih, Windows DDK MVP
    StorageCraft Corporation
    maxim@storagecraft.com
    http://www.storagecraft.com



  14. Re: Cheap Way To Share Fibre Channel Storage


    "Will" wrote in message
    news:QeSdnclA6KiP4DHfRVn-rw@giganews.com...
    > No, our application is write once every two weeks, but read
    > 10,000 times a day. We don't need to track writes to the disk,
    > and on those days when writes take place, the readers can simply
    > be rebooted.


    If you are going to manually reboot every time the writer "writes" then you
    might get away with this approach, anything else is likely to lead the
    "readers" into random blue screens (well more random than normal :-) as they
    occasionally get inconsistent data from what they *believe* is a read-only
    device.

    Silly question, but why not serve the disks up to the "writer" and share it
    from so that the readers access via a network share?


    --
    Nik Simpson



  15. Re: Cheap Way To Share Fibre Channel Storage

    It's a good question, but it was just my assumption that the network
    introduces latency on each operation. When you need to open thousands of
    files quickly every 10 ms delay per file adds up.

    --
    Will
    Internet: westes AT earthbroadcast.com


    "Nik Simpson" wrote in message
    newsYnre.119010$J25.35983@bignews6.bellsouth.net...
    > Silly question, but why not serve the disks up to the "writer" and share

    it
    > from so that the readers access via a network share?
    >
    >
    > --
    > Nik Simpson
    >
    >




  16. Re: Cheap Way To Share Fibre Channel Storage

    Will napisał(a):
    > I'm looking for a cheap way to have more than one computer share
    > read-only access to fibre channel storage under Windows 2000.
    > I'm using Compaq fibre channel arrays for the hardware, and those
    > are fine for low-end use, but they don't have any option
    > internally to give read-only access. A host is designated in
    > the Compaq software as either having full access or no access.
    > If multiple Windows hosts try to write to the same logical
    > device, they will trash sensitive file system structures on the
    > disk.
    >
    > Is there any low-priced software that would run as a service on
    > Windows that would prevent any attempt to write to designated
    > disks? The service would need to be fairly low level and would
    > need to prevent the Windows kernel from writing to the disk.
    >

    Maybe Tivoli SANergy software would help you - but I'm not sure if it's
    Cheap ;-).
    http://www-306.ibm.com/software/tivo...ducts/sanergy/

    Huba

  17. Re: Cheap Way To Share Fibre Channel Storage


    "Will" wrote in message
    news:i_KdnRCBR4SzjjPfRVn-gQ@giganews.com...
    > It's a good question, but it was just my assumption that the network
    > introduces latency on each operation. When you need to open thousands of
    > files quickly every 10 ms delay per file adds up.


    I'd certainly be tempted to give it a try, if it works, its a lot easier
    than trying to share the device via the SAN without using software designed
    for that purpose.


    --
    Nik Simpson



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