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Fail-safe UWF overlay size? RRS feed

  • Question

  • I am using UWF disk-based overlay on Win 10 IOT ENT to protect my c: operating system volume except for a few file and registry exclusions. If I set the overlay size to half of the partition size, am I guaranteed to never exhaust the overlay?

    Wednesday, August 10, 2016 6:48 PM

All replies

  • The max overlay size is 1GB. Depends on your system operation if the overlay gets filled. Did you open holes for .NET Assemblies, WinSXS folder , and event logs?

    Sean Liming - Book Author: Starter Guide SIM (WEI), Pro Guide to WE8S & WES 7, Pro Guide to POS for .NET - www.annabooks.com / www.seanliming.com

    Wednesday, August 10, 2016 10:04 PM
    Moderator
  • The max overlay size is 1GB. Depends on your system operation if the overlay gets filled. Did you open holes for .NET Assemblies, WinSXS folder , and event logs?

    Sean Liming - Book Author: Starter Guide SIM (WEI), Pro Guide to WE8S & WES 7, Pro Guide to POS for .NET - www.annabooks.com / www.seanliming.com

    1GB??? That doesn't seem right. The following says 16 terabytes:
    https://msdn.microsoft.com/en-us/library/windows/hardware/mt571992(v=vs.85).aspx

    I've used uwfmgr to set mine to set 25GB without error, and uwfmgr get-config reported it back to me. I can't say that I've actually exercised it, though 

    OVERLAY SETTINGS
        Type:               Disk
        Maximum size:       25000 MB
        Warning Threshold:  24000 MB
        Critical Threshold: 24500 MB

    I opened holes for the event logs and some things custom to my application, but not .NET and WinSxS. I really want to protect as much of the OS as possible. 

    My impression is that UWF images all writes to the protected volume in a pre-allocated overlay file. Writes to excluded items are also written to the volume itself. If this is so, then I reason that allocating half the volume to the overlay file would guarantee that, even if every non-overlay sector of the volume is written, the overlay file is large enough to image them without overflow. Am I understanding this correctly?

    Wednesday, August 10, 2016 10:55 PM
  • I think that is the size of the volume it can protect not the overlay size itself.

    A little later it states for disk overlays - Disk-based overlays require a "Maximum Overlay Size" of 1024 KB.

    If you look at the other UWF posts, you will see that all writes including those made to the open holes are sent through the overlay, thus UWF overlay can get filled up.


    Sean Liming - Book Author: Starter Guide SIM (WEI), Pro Guide to WE8S & WES 7, Pro Guide to POS for .NET - www.annabooks.com / www.seanliming.com

    Wednesday, August 10, 2016 11:42 PM
    Moderator
  • This is news to me,

    Do you really need holes for that .net abomination?

    WinSXS is one I don't have either. Although I did manage to shrink it by almost 4Gb with judicious use of DISM. Since I don't have windows update working in the field, I *shouldn't* need this one, right?

    And yes, I do have eventlogs, BCD0000000 etc.


    =^x^=

    Monday, August 15, 2016 11:47 PM
  • The .NET caught me off guard with several clients. Not everything gets optimized right away, even if I force NGEN to run. Better to open the hole.

    Sean Liming - Book Author: Starter Guide SIM (WEI), Pro Guide to WE8S & WES 7, Pro Guide to POS for .NET - www.annabooks.com / www.seanliming.com

    Tuesday, August 16, 2016 1:01 AM
    Moderator