SMB low level details RRS feed

  • Question

  • I'm tracking down an issue with reading files being very slow over the network (using Vista).  I'm tracing the system file I/O calls using Perfmon and see a couple oddities I'd like to ask about:

    1. I see a ReadFile followed by a FASTIO_CHECK_IF_POSSIBLE.  They are for the same size and offset.  Why two calls to get the data for every read done in the application?

    2. I see extra ReadFile's that I'm not making that read in an extra 32,768 bytes.  The flags on the ReadFile are I/O Flags: Non-cached, Paging I/O, Synchronous Paging I/O, Priority: Normal.  What are these?  Looks like some type of caching but I'd like to disable it.

    What forum should I ask on to get answers to these low level kernel and SMB filesystem questions?
    Saturday, January 9, 2010 5:11 AM