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EWF with screen saver issue RRS feed

  • Question

  • Hi everyone,

     I got problem when using ewf, the scenario is like this:

     1. turn EWF on, target disk is C:

     2. Edit an existing text file(for example C:\abc.txt) using notepad, save the changes, exit notepad.(DO NOT use "ewfmgr c: -commit" command)

     3. Wait unitl the screen saver starts.

     4. Cut off the power supply while screen saver is on.

     5. Plug in the power cord, start the machine.

     6. check the text file that have been changed.

    Expected result: the changes on the file do not take effect(because we didn't commit the changes), the file content is the same as its original content.

    Actual result: the text file's content is full of "NULL" vaule, and if we open it with notepad, it is full of "0".

    Enrionment: Processor: Intel I7 740

                      Harddisk: Intel SSDSA2CT040G310.

                      OS: Windows Embedded Standard 7

    I wonder what happend when the system enters screen saver mode, and if the machine is not in screen saver mode , the actual result is the expected result.

    I hope someone can help me

    Thank you very much

    -Haibo

    Thursday, June 30, 2011 7:46 AM

Answers

  • Sorry to reply so late.

    With EWF disabled, the issue will not happen.

    And after some research and searching on the internet, found that the SSD's TRIM feature and WES7's EWF feature don't cooperate well.

    The work around is to turn off TRIM.

    But it is still a problem for MS and Intel to give a solution on EWF and TRIM.

    • Marked as answer by haibo Friday, August 26, 2011 7:08 AM
    Tuesday, July 26, 2011 10:05 AM

All replies

  • When you turned EWF on, did you do a reboot?

    -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
    Thursday, June 30, 2011 5:09 PM
    Moderator
  • Sean,

      thanks for your reply. after executing "ewfmgr c: -enable" command, I restarted the machine.

    Tuesday, July 5, 2011 2:58 AM
  •  

    I am not following - did this work?

    What is EWF setup for RAM or RAM-REG?

     

    -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
    Tuesday, July 5, 2011 4:15 PM
    Moderator
  • the EWF is working in RAM-REG mode.

    and it works fine except the case that I posted above (cut off power supply while screen saver).

    any idea about this ?

     

    thanks,

    Haibo

    Saturday, July 9, 2011 4:07 AM
  • EWF and power failure has been an interesting topic. Even though EWF is protecting the flash drive, corruption can still occur. When you are running from a flash disk, flash disk implement wear-leveling. If you are using NTFS, NTFS  adds an issue with meta data section, which is not protected by EWF, so writes are being made directly to the disk. The address lines on the controller still get toggled when you make a write and can trigger a wear-leveling to move blocks around. If blocks are being moved when power is cut off, you could get corruption, but the meta data section is supposed to help mitigated. I have had some customers try to use FAT instead of NTFS, and the disk got corrupted where the OS wouldn't boot. When they switched to NTFS, cutting the power wasn't a problem.

    Your issue is new and a different twist on the filter puzzle. If you do a normal shutdown after the screen saver and resart the system, is the file contents what you would expect? If you cut the power before the screen saver, what happens to the file?

    -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
    Saturday, July 9, 2011 6:11 PM
    Moderator
  • Hi Sean,

    Thanks for explaining EWF!

    to what you asked:

    1. if I do a normal shutdonw after the screen saver, the file contents got corrupted as well.

    2. if I cut the power before the screen saver, the file content is still the one before edited, this is the expected result.

    so I wonder what the OS did during the screen saver .

     

    PS:

    If I turn off the monitor instead of entering screen saver, the result is the same.

     

    -Haibo

    Monday, July 11, 2011 2:35 AM
  • This is new. With EWF disabled what happens?

    -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
    Monday, July 11, 2011 4:34 AM
    Moderator
  • Sorry to reply so late.

    With EWF disabled, the issue will not happen.

    And after some research and searching on the internet, found that the SSD's TRIM feature and WES7's EWF feature don't cooperate well.

    The work around is to turn off TRIM.

    But it is still a problem for MS and Intel to give a solution on EWF and TRIM.

    • Marked as answer by haibo Friday, August 26, 2011 7:08 AM
    Tuesday, July 26, 2011 10:05 AM
  • I know this is old but still interessting. Are there any new Information?
    Or is it at least confirmed that it is realted with TRIM?

    Windows Embedded Developer and Scripting Guy //Germany (http://www.wesnext.com)


    • Edited by KNARZ Wednesday, January 15, 2014 3:47 PM
    Wednesday, January 15, 2014 3:46 PM