Cached/noncached coherency over redirector

NTFSD
1

Hi,

I have a very serious problem with cached/noncached requests
going over the redirector.

My filter sends a noncached write to the redirector
(initiated by the LazyWriter). On the other side
(on the server machine), I see a normal cached
write. This is probably translated by the srv.sys.
But if I use IoSynchronousPageWrite, the write requests
goes noncached even over the redirector.

Can anyone tell me why the redir/srv translates the
LazyWriter requests to the cached writes ?

L.

2

If I’m reading your question correctly, you are seeing all IO on the
server-side of the IO path as buffer. That is the expected behavior.

SRV always strips off the NO_BUFFERING bit as it opens handles on the
server, therefore all the IO done on the server side should be cached
(even if it was unbuffered, paging IO on the client). This is done for
performance reasons as SRV wants to make use of the system cache on the
server to be able to return file data as fast as possible.

Regards,

Molly Brown
Microsoft Corporation

This posting is provided “AS IS” with no warranties and confers no
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-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com] On Behalf Of Ladislav Zezula
Sent: Tuesday, July 13, 2004 2:28 AM
To: Windows File Systems Devs Interest List
Subject: [ntfsd] Cached/noncached coherency over redirector

Hi,

I have a very serious problem with cached/noncached requests
going over the redirector.

My filter sends a noncached write to the redirector
(initiated by the LazyWriter). On the other side
(on the server machine), I see a normal cached
write. This is probably translated by the srv.sys.
But if I use IoSynchronousPageWrite, the write requests
goes noncached even over the redirector.

Can anyone tell me why the redir/srv translates the
LazyWriter requests to the cached writes ?

L.

Questions? First check the IFS FAQ at
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3

I am not surprised that the srv.sys is issuing ‘buffered’ writes to the FSD
on the Server machine. This is because srv.sys wants to get maximum
performance by utilizing the caching on the server machine. Actually srv.sys
will use MDL based read/writes to tranfer data in/out of the cache directly
to/from the network.

Manish

“Ladislav Zezula” wrote in message news:xxxxx@ntfsd…
> Hi,
>
> I have a very serious problem with cached/noncached requests
> going over the redirector.
>
> My filter sends a noncached write to the redirector
> (initiated by the LazyWriter). On the other side
> (on the server machine), I see a normal cached
> write. This is probably translated by the srv.sys.
> But if I use IoSynchronousPageWrite, the write requests
> goes noncached even over the redirector.
>
> Can anyone tell me why the redir/srv translates the
> LazyWriter requests to the cached writes ?
>
> L.
>
>
>
>