NTFS and FAT32 sending requests to a Write-Protected SCSI LUN

NTFSD
1

Hi All,
I have a SCSI target and exposing one LUN , which is either formatted with NTFS or FAT32.
For some purpose , I have to “Write Protect” this LUN.
This is done by setting the SWP bit in ModeSense6 SCSI command.

When Windows boots, the SCSI initiator, sends the modesense6 command and gets
this attribute that my LUN is write protected. But still, the filesystem sends a write
request on this write protected LUN, inspite of knowing that it is Read only.

If I explicitly try to create a folder or file on this LUN(windoes volume), filesystem gives
the error that “media is write protected”.

Could someone please give me the reason as to why does the filesystem(both NTFS and
FAT32) continue sending write request on Write Protected volume?

Regards,
Priya.

We won’t tell. Get more on shows you hate to love
(and love to hate): Yahoo! TV’s Guilty Pleasures list.
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2

What OS are you running on initiator side? Earlier versions of Windows (up
to 2000) do not understand
read only hard disks. At all. For XP and up you can have read only NTFS
however. AFAIK.

In any case the whole idea is broken. You cannot make compatible RO hard
disk this way. The only 100%
working solution would be to ALLOW writes but keep some sort of the mirror
cache for them. So after
reboot/disk unmount you’ll have all your original data back again. Something
close is done in StorageCraft
ShadowStor or whatever they call it now product (with the only difference -
they use disk filter instead
of iSCSI initiator for loopback configuration). And this is *exactly* what
we do inside our own iSCSI target.
Works fine with ANY OS at initiator side. Proven by years. Just clone!

Regards,
Anton A. Kolomyeytsev

CEO, Rocket Division Software

-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com] On Behalf Of priya sehgal
Sent: Thursday, March 22, 2007 3:16 PM
To: Windows File Systems Devs Interest List
Subject: [ntfsd] NTFS and FAT32 sending requests to a Write-Protected SCSI
LUN

Hi All,
I have a SCSI target and exposing one LUN , which is either formatted with
NTFS or FAT32.
For some purpose , I have to “Write Protect” this LUN.
This is done by setting the SWP bit in ModeSense6 SCSI command.

When Windows boots, the SCSI initiator, sends the modesense6 command and
gets
this attribute that my LUN is write protected. But still, the filesystem
sends a write
request on this write protected LUN, inspite of knowing that it is Read
only.

If I explicitly try to create a folder or file on this LUN(windoes volume),
filesystem gives
the error that “media is write protected”.

Could someone please give me the reason as to why does the filesystem(both
NTFS and
FAT32) continue sending write request on Write Protected volume?

Regards,
Priya.

We won’t tell. Get more on shows you hate to love
(and love to hate): Yahoo! TV’s Guilty Pleasures list.
http://tv.yahoo.com/collections/265

Questions? First check the IFS FAQ at
https://www.osronline.com/article.cfm?id=17

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3

> Could someone please give me the reason as to why does the filesystem(both

NTFS and
FAT32) continue sending write request on Write Protected volume?

The main reason of such behavior are errors in a locked buffers processing
that result in a durty flag setting for PFNs describing the physical pages
backing these locked buffers. For example, creating an MDL for a read buffer
and locking it with IoWriteAccess or IoModifyAccess results in marking the
pages as dirty and the subsequent write requests.

–
Slava Imameyev, xxxxx@hotmail.com

“priya sehgal” wrote in message news:xxxxx@ntfsd…
> Hi All,
> I have a SCSI target and exposing one LUN , which is either formatted with
> NTFS or FAT32.
> For some purpose , I have to “Write Protect” this LUN.
> This is done by setting the SWP bit in ModeSense6 SCSI command.
>
> When Windows boots, the SCSI initiator, sends the modesense6 command and
> gets
> this attribute that my LUN is write protected. But still, the filesystem
> sends a write
> request on this write protected LUN, inspite of knowing that it is Read
> only.
>
> If I explicitly try to create a folder or file on this LUN(windoes
> volume), filesystem gives
> the error that “media is write protected”.
>
> Could someone please give me the reason as to why does the filesystem(both
> NTFS and
> FAT32) continue sending write request on Write Protected volume?
>
> Regards,
> Priya.
>
>
>
>
>
>
>
> ____________________________________________________________________________________
> We won’t tell. Get more on shows you hate to love
> (and love to hate): Yahoo! TV’s Guilty Pleasures list.
> http://tv.yahoo.com/collections/265
>