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Write Filter Question RRS feed

  • Question

  • I dont know much about write filters and not even sure if I need to use them. I've read and read and still cant get my head wrapped around them. If you can point me to an easy to read breakdown of them please do so.

    But right now, I'm not using any write filters. I just toss in FBWF, because EWF w/HORM conflicts with windows boot environment.

    Our machines use SQL and are constantly writing and reading to the DB, I dont ever need this to be wiped out (as I read a write filter saves the writes until you restart).

    So is there any benefit to using a write filter, any performance benefit? and which one should I use? Is it hurting anything have FBWF installed and not using it?

     

    Friday, October 14, 2011 4:06 PM

All replies

  • Sean will probably be better at explaining these but...

    The benefit of a write filter is protection. It will protect the OS against corruption, accidental screw ups and viruses. It will also help if you are using Solid State Media for your hard drive, because it Solid State Media has limited write capabilities you do not want the OS constantly writing to it when it doesn't need to. So instead the write filter will write the data to the RAM instead until you tell it to commit the written files to the hard drive.

    Having FBWF in the image without using it does not hurt anything. If in your case you want to constantly write to a database and have FBWF enabled and protecting the OS, you can designate directories that FBWF will not protect.

    Hope this helps.


    "Learning without thought is labor lost; Thought without learning is perilous." Confucius
    • Proposed as answer by Sean LimingMVP Friday, October 14, 2011 4:49 PM
    Friday, October 14, 2011 4:41 PM
  • ok, now that makes the most sense of anything I've read so far. We do use Compactflash cards in the panel PC's. And now that I know you can specify specific directories that you want excluded I may be interested in this.

     

    Do they offer any sort of performance gain? Especially since our units are sent out with the max 2GB of RAM.

    Friday, October 14, 2011 4:44 PM
  • In the time that I've used them they do not offer any performance gains. But they can cause issues if there is too much data being written to the RAM. For example if you didn't exclude one of the directories that the database writes to, after awhile the RAM will start to fill up and there will be less RAM for the system to use for itself. So if you are aware of this at the beginning then you can easily find the culprit of the problem and unlock that directory as well.

    And again this is just from my experience, others might have seen different results or have different uses for the filters.


    "Learning without thought is labor lost; Thought without learning is perilous." Confucius
    Friday, October 14, 2011 4:52 PM
  • When the book arrives, look at the write filter introduction and FBWF. Performance is subjective. Processor speed, memory, and boot media all play a roll in system performance. If the application is in .NET, using ngen.exe to convert ot native code has been recommended.

    The filters are not going to help with performance, but with reliablility / stability of the system. Osolith pointed out the basic reasons. The filters are not perfect, but they do provide a level of protection.

    -Sean


    www.sjjmicro.com / www.seanliming.com / www.annabooks.com, Book Author - ProGuide to WES 7, XP Embedded Advanced, WEPOS / POS for .NET Step-by-Step
    Friday, October 14, 2011 4:57 PM