DosQueryPathInfo speed - OS2

This is a discussion on DosQueryPathInfo speed - OS2 ; What is the performance comparison of using DosQueryPathInfo to retrieve information in an EA versus a seek into a file (usually less than 8k from SEEK_SET) and read the data?...

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  1. DosQueryPathInfo speed

    What is the performance comparison of using DosQueryPathInfo to retrieve
    information in an EA versus a seek into a file (usually less than 8k
    from SEEK_SET) and read the data?







  2. Re: DosQueryPathInfo speed

    Hi,

    Bill Silverstein schrieb:
    > What is the performance comparison of using DosQueryPathInfo to retrieve
    > information in an EA versus a seek into a file (usually less than 8k
    > from SEEK_SET) and read the data?


    the Answer will obviously depends on the filesystem.

    In case of HPFS and small EAs, the EAs are probably faster, because they
    are stored directly in the FNODE. With more than a few hundred bytes of
    EAs this will change, because the information resides then in seperate
    extents, as the file content does too.
    Other filesystems behave different. FAT will always allocate a separate
    cluster for EAs. NTFS stores any content that fit into the remaining
    space of the 4k block without a separate allocation (ACLs, EAs, file
    content).
    JFS: don't know any details.
    And if you are working over a network, the network protocol (Probably
    LANMAN2) and the server filesystem will contribute. The protocol
    overhead is less with EAs, but this is probably not the limiting factor.
    The disk access time will be the main contribution. Of course, if your
    storage device will not have a high access time (e.g. a flash disk)
    everything will change again.


    Marcel

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