EWF Disk Mode RRS feed

  • Question

  • I have some HP thin-client where Windows 10 Enterprise LTSB custom image is installed. These clients having 4 GB RAM is installed and 2.9 GB is usable because of video memory.

    As we know in the write filter environment all writes are in overlay and system must reboot to clear the overlay memory otherwise system will get crashed after overlay exhausted.  

    In this OS we have only one drive C which is protected by UWF and additional drive Z which is RamDisk for temporary writes and maximum of 768 MB, so its not possible to create page file in protected volume because while enabling UWF page file don't exist any more and the other drives are Z very less in memory.

    Now using some tool while booting OS, i have moved 8GB of partition from c drive and created additional drive D which is not protected then configured page file range 4.5 GB to 7GB in this drive after enabling the UWF still page file present and working.

    Because of low RAM, Is it good to Use UWF disk mode instead of UWF RAM and how to configure ?

    Now i have know UWF overlay size and how to calculate the system UP time which is depend upon the size of the overlay size.

    Is it good to set 600 MB or 1000 MB for overlay size and what are the UP times, now system is not complete running as i can see in it used overlay memory in 2 days around 100 mb ?

    Thanks in advance. 

    Thursday, September 13, 2018 7:35 AM


All replies

  • Hey, I have configured my system with UWF disk based overlay and max overlay size set to 5 GB, apart from this i also have D volume unprotected with page file. Is it good to use UWF disk based overlay with page file ? because i have seen in Microsoft document it says: " UWF also supports the use of paging to increase virtual memory, if the page file exists on an unprotected volume. When paging is used together with a RAM-based overlay, the uptime of the system can be significantly increased"

    Thanks in advance!

    Thursday, September 13, 2018 9:08 AM
  • As stated in, a disk overlay should have a size of at least 1024MB.

    Using both - UWF disk overlay and page file - should not be a problem since the page files must be located on an unprotected volume - therefore paging operation should not be interferred by UWF.

    Using a disk overlay - in my opinion - is a last resort since disk I/O is very much slower than RAM, this impacts the all over performance significantly. What about the RAM disk you are using - is it really required that your temporary data are kept there, or is it possible to write them to an unprocted volume?

    Regarding overlay consumption you may use ProcessExplorer or similar tool to find out which process(es) causes disk I/O - maybe you'll find a way to reduce this and  - in turn - increase your UP time.

    Willi K.

    Thursday, September 13, 2018 9:43 AM
  • Hi Wili,

    In my setup 2.9 Gb is usable memory and 4 GB is physical memory installed and 1.1 Gb for video memory.

    I have tested two cases:

    1. Using UWF RAM-based overlay where i set overlay size is 600 MB and i found around 1 GB RAM is free for system using but in this case if use less overlay size because dont have enough RAM then system up time less and i think we need reboot around 1 week but we dont want regular reboot.

    1b. If i increase overlay size 1024 then i found for system 800 MB is free.

    2. In this case i use disk-based overlay where i set overlay size which uses system volume but in this case if overlay size is 5 GB then no need of regular reboot but the thing is that disk overlay is much slower than RAM overlay.

    According to your opinion which one is a good solution for good performance ?

    I think 1a is also good but the thing is that after that we have 800 mb left for the system but in all cases unprotected disk D with page file.

    Thursday, September 13, 2018 10:09 AM
  • As already mentoined, a RAM based overlay would be best choice. Once data in the protected have been modified, they are cached in the overly by UWF (=RAM overlay stores faster) and therefore can be read much faster.

    Since you are in trouble because of low RAM I suggest to prefer disk overlay for UWF and try to get system running without a page file if possible. If you need the page file you need to configure it's location to the unprotected voluem D (due to UWF).

    Again, also try to get rid of the RAMDisk (Z) to get more RAM for the system. 

    Thursday, September 13, 2018 12:07 PM
  • Hi  Willi,

    Yes i can understand RAM based overlay is faster but the thing is we don't have enough RAM available.

    I will try to set as you said disk overlay in one of the client but the thing is that system performance will effect. Is it really noticeable or disk overlay can also use if shortage of RAM. 

    yes i have decreased RAMdisk (Z) to 100 MB. 


    Thursday, September 13, 2018 1:51 PM
  • The performance impact is based on the system + application. You just have to try it and see what happens. Moving to Disk Overlay in your case would help to free up memory.

    This is a Windows 10 question posted to the XP Embedded forum. Do you mind if I move it to the proper forum?

    Sean Liming - Book Author: Starter Guide Windows 10 IoT Enterprise - /

    Thursday, September 13, 2018 7:02 PM
  • Hi Sean,

    I will also try to test disk overlay. Yes in my case disk overlay is good solution.

    Sorry i don't know its XP forum, i thought its embedded by the way you can move to proper forum i dont mind at all.

    Thanks for the information!

    Friday, September 14, 2018 6:37 AM
  • Hi Sean,

    I have one question regarding overlay memory monitoring, i know there is icon in windows notification area, if that icon background is yellow then its already reached to threshold level but these all about with admin account but if the user is using in kiosk mode and they don't have something notification area then how to know ?

    Is it possible to monitor overlay memory via monitoring solution or is there any script ?

    Friday, September 14, 2018 8:43 AM
  • A custom app could be created using the UWF WMI API to monitor the memory consumption.

    Sean Liming - Book Author: Starter Guide Windows 10 IoT Enterprise - /

    Friday, September 14, 2018 2:30 PM
  • Hi,

    Could you please help me out how to create UWF WMI API?

    Actually locally by going to every hosts, we can easily see the overlay consumption by command line and inbuilt GUI tool. But i need a script that could be integrated with monitoring solution check mk, so like other services we can also monitor UWF overlay size and its consumption. 

    Thanks in advance.

    Monday, September 17, 2018 12:48 PM
  • There is an example here:

    Sean Liming - Book Author: Starter Guide Windows 10 IoT Enterprise - /

    • Marked as answer by sshami Wednesday, September 19, 2018 6:08 AM
    Tuesday, September 18, 2018 5:51 PM
  • Thanks a lot!
    Wednesday, September 19, 2018 6:08 AM