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Home > Archive > Data Storage > June 2005 > Cheap Way To Share Fibre Channel Storage
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Cheap Way To Share Fibre Channel Storage
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| 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
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| palomina 2005-05-28, 8:45 pm |
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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" <DELETE_westes@earthbroadcast.com> 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.
| |
| Eric Gisin 2005-05-29, 2:45 am |
| <palomina> 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.
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| 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
<palomina> 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.
| |
| Maxim S. Shatskih 2005-05-29, 5:49 pm |
| > 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
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| 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
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| Jon Metzger 2005-05-31, 7:46 am |
| 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.
| |
| Brook Reams 2005-06-11, 5:46 pm |
| 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" <jon_dot-metzger@_gmail_.com> wrote in message
news:d7hmrp$5bp$1@lenny.tc.umn.edu...
> Will wrote:
>
> cisco MDS switches support read-only zones. I believe its a licensed
> feature. Not exactly cheap if you don't already own cisco fibre channel
> switches, but I thought it was worth mentioning.
| |
| Nik Simpson 2005-06-12, 7:45 am |
|
"Will" <DELETE_westes@earthbroadcast.com> wrote in message
news:GqqdnV_F9pR6VwXfRVn-1Q@giganews.com...
>
> Is there any low-priced software that would run as a service on
> Windows that would prevent any attempt to write to designated
> disks? The service would need to be fairly low level and would
> need to prevent the Windows kernel from writing to the disk.
Even if such a utility exists, it will not help you because you need all the
systems in "share" group to be aware of writes, even if only one of them is
allowed to write. The reason is that the read-only machines may get stale
data from the disk because the "writer" has cached writes not yet committed
to disk that may impact filesystem structures or file content. You could
also get problems with writes that are partially complete when one of the
readers tries to read.
The only way this can be done safely is with a shared filesystem designed
for the task. On Windows you should look at Tivoli SANergy as possible
solution, see
http://www-306.ibm.com/software/tiv...oducts/sanergy/
--
Nik Simpson
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| No, our application is write once every two weeks, but read
10,000 times a day. We don't need to track writes to the disk,
and on those days when writes take place, the readers can simply
be rebooted.
I really do need something very very simple.
--
Will
Internet: westes at earthbroadcast.com
"Nik Simpson" <n_simpson@bellsouth.net> wrote in message
news:pbWqe.117372$J25.6212@bignews6.bellsouth.net...
>
> "Will" <DELETE_westes@earthbroadcast.com> wrote in message
> news:GqqdnV_F9pR6VwXfRVn-1Q@giganews.com...
on[vbcol=seagreen]
would[vbcol=seagreen]
>
> 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/tiv...oducts/sanergy/
>
>
> --
> Nik Simpson
>
>
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| David A.Lethe 2005-06-13, 5:47 pm |
| On Sun, 12 Jun 2005 11:21:05 -0700, "Will"
<DELETE_westes@earthbroadcast.com> 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.
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| Maxim S. Shatskih 2005-06-13, 5:47 pm |
| > 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
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| Nik Simpson 2005-06-13, 5:47 pm |
|
"Will" <DELETE_westes@earthbroadcast.com> 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
| |
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| 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" <n_simpson@bellsouth.net> wrote in message
news:pYnre.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
>
>
| |
|
| 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/tiv...oducts/sanergy/
Huba
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| Nik Simpson 2005-06-14, 7:46 am |
|
"Will" <DELETE_westes@earthbroadcast.com> 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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