FASTIO_READ vs IRP_MJ_READ

Discussion in 'Windows Networking' started by martin.roclawski, Jun 13, 2005.

  1. Can someone please tell me what governs these calls. We have software
    that acessess a file share on the server and if it uses IRP_MJ_READ it
    is terribly slow. I understand why it is slow I just do not understand
    what governs which call will be used.

    Can anyone Help?
     
    martin.roclawski, Jun 13, 2005
    #1
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  2. martin.roclawski

    Todd J Heron Guest

    What controls it is whether or not the data is in the file system cache or
    not. Cached data is read by a FASTIO_READ while non-cached data is a slower
    IRP_MJ_READ. Whenever a file system driver returns a Fast I/O command
    status of FALSE, the I/O Manager falls back on the IRP-based request path.

    http://www.windowsitpro.com/Windows/Articles/ArticleID/4795/pg/2/2.html
     
    Todd J Heron, Jun 13, 2005
    #2
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  3. Todd thanks for the reply - I sort of knew that bit already - my
    mistake I should have been more explicit.

    In a client - server file share scenario which file system should we be
    looking at? The reason I ask is we have two setups running WinXP
    Clients and Win2003 Servers. One uses FASTIO_READ while the other uses
    IRP_MJ_READ. This obviously causes the software to run significantly
    slower and while we know what the issue is we don't know how to change
    the setup so the FASTIO_READ is used or even if it is possible to
    control this at all?
     
    martin.roclawski, Jun 14, 2005
    #3
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