in reply to Re: Seeking general directions for a Windows specific app
in thread Seeking general directions for a Windows specific app

The filesystem, system caches and disk DD's have access to far more and far better information, from all concurrent activity--not just those processes using your mechanisms--upon which to decide what order to read and write things and when.

I personally believe that this seems to be the general consensus as of the answers that popped up in this thread. I may well stand corrected out of trusting the expertise of you all. But the impression of things getting so awfully slow with parallel transfers was so strong that I'd like to at least do some (more) experiment and to this end...

However, were I to write something along these lines, my starting point would be Jenda's extremely useful Win32::FileOp, which gives you direct access to the OS's own MoveFile and CopyFile functions

...I will certainly try Win32::FileOp in the first place to do the experiment in a more controlled way! Thank you for the suggestion!

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Re^3: Seeking general directions for a Windows specific app
by BrowserUk (Patriarch) on Aug 14, 2008 at 22:33 UTC

    One thing to consider, is the source and quality of your USB device driver. Many moons ago when evaluating a 8-port serial card (under OS/2), we found that every additional concurrent transfer halved the overall combined throughput until by the time we had all 8 ports transferring data concurrently, the combined throughput was almost at a crawl.

    As we were potentially going to be purchasing many hundreds of these cards, the manufacturers sent us a support technician to help us resolve the problem. Turned out that the install had selected to use a generic serial port driver rather than the manufacturer supplied one. And as that had been written to deal with just the standard 2-port configuration, it was overly conservative in its design and that was the cause of the abysmal throughput.

    Once we installed the serial DD designed to deal with the 8-port device, things improved immensely. I'd strongly suggest that you visit the web site for whoever manufactured your USB card and check the availability of the latest drivers. Also, if you installed anything involved in the USB stick using Plug&Pray, check that it used the manufacturers DDs and not generic ones. Especially if your copy of Windows is relatively old. Early builds shipped with only USB v1.x drivers, but most devices work much better with later v2.x drivers.

    The availability and capabilities of DDs always trail the hardware.

    Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
    "Science is about questioning the status quo. Questioning authority".
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