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Windows 10 Mirror Disk not showing in boot menu [SOLVED]

    Question

  • I am hoping that someone in this forum can either answer this question or refer me to an expert at Microsoft who can. I previously asked the question in this thread back on April 7, 2017 with no success. Then I opened a support call on the same subject and three different MS support engineers still could not help. At the moment, I am waiting for "escalation".

    The problem is very specific and repeatable.

    On a Windows 10 Pro system with dual 250GB SSDs, when mirroring the Windows partition using software mirroring the second disk is not added as a menu choice in the BCD. There is an error message generated that says

    Image

     

    The mirroring completes and everything look normal but there is no entry added to the BCD Store. Disk Management shows

    Image.

    BCDEdit shows

    Image

    When this process works correctly, as proven in hundreds of Windows workstations and servers over many years, the following happens: 

    • Install Windows on the Primary Disk.
    • Open Disk Management, select the System Reserved partition, select Add Mirror, select the Secondary Disk, wait for partitions to finish sync.
    • Select the Windows OS partition, select Add Mirror, select the Secondary Disk.
    • No error message is generated and the OS partitions start resynching.
    • The BCD Store is automatically updated and adds a new Windows Boot Loader entry with a different GUID from the entry for the Primary Disk and the words “- Secondary Plex” added to the description.
    • Since the System Reserved partition is mirrored, this entry is added to both disks simultaneously.
    • In the future, if either OS partition is unbootable for any reason, or if either disk fails for any reason, the boot menu with BOTH CHOICES is shown and the system can be started. Both menu choices are shown regardless of which disk the system starts from because the “System Reserved” partition is mirrored. If any changes are made (replacing/upgrading a disk, breaking the mirror and then having to reestablish the mirror for some reason) there is only one BCD Store to update.

    Here is an example from a Windows 10 System that is working correctly. The partition layout of the operating system disks is similar to the Windows 10 partition layout shown above (mirrored System Reserved and mirrored Windows OS partitions).

    


    I have looked at permissions for the BCD Store on a working system and on the problem machine and they are identical. I have even tried to run “Disk Management” and the command line “DiskPart” using the machine account “$PCName” rather than just the Administrator account. Nothing works. I have rebuilt the machine and reinstalled Windows multiple times. I have even (with Microsoft Support connected via LogMeIn) removed the mirror and then remirrored the drives to show the specific error message. Nothing has worked so far.

    Any assistance would be greatly appreciated. 


    • Edited by jdz.tsg Friday, April 28, 2017 12:34 PM solved
    Thursday, April 27, 2017 1:06 AM

Answers

  • This issue is resolved.

    The solution is

    1. Boot to the recovery environment.
    2. Break the mirror using DiskPart.
    3. Rebuild the BCD using BootRec /RebuildBCD.
    4. Boot back into Windows on the Primary Disk.
    5. Delete the partitions from the Secondary Disk.
    6. Remove the old entry for the Secondary Disk from the BCD using BCDEdit.
    7. Remirror the Primary back onto the Secondary (System Reserved and Windows OS partitions).
    • Marked as answer by jdz.tsg Friday, April 28, 2017 12:34 PM
    Friday, April 28, 2017 12:34 PM

All replies

  • Hi jdz.tsg,

    Please refer to the following link's document to update the BCD manually.
    Tip of the Day: Configuring Disk Mirroring for Windows Server 2012
    https://blogs.technet.microsoft.com/tip_of_the_day/2014/10/10/tip-of-the-day-configuring-disk-mirroring-for-windows-server-2012/

    Please note the difference between BIOS and UEFI. I have tried those steps on my Windows 10 machine and it could work well.

    Best regards

    Please remember to mark the replies as answers if they help.
    If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com.

    Thursday, April 27, 2017 9:54 AM
    Moderator
  • Thank you for your response.

    However, the article that you refer to does not address my issue. That document is detailing a very complex procedure to manually create a completely different "System Reserved" partition on the Secondary Disk which then has to be updated manually in the future. For some reason, it ignores the simple configuration where the "System Reserved" partition is mirrored and both disks are updated at the same time.

    IF I was going to try and manually update the BCD like the error message says, I would need instructions about how to add a secondary mirrored OS partition as a DIFFERENT BCD entry - the same way that it is (normally) automatically done by Windows when adding a mirror partition in Disk Manager.

    The problem is, as you can see above in the example from a properly working system with a boot menu, the BCD entries for both Primary and Secondary appear identical except for the identifier. They both point to "partition=C:" for the device and the osdevice.

    I would create the secondary entry as a workaround if I knew how.

    But what I really need to find out is WHY this isn't working automatically. WHY can't the system update the Boot Configuration Data? What is causing the error message in the first place?

    Thursday, April 27, 2017 11:43 AM
  • This issue is resolved.

    The solution is

    1. Boot to the recovery environment.
    2. Break the mirror using DiskPart.
    3. Rebuild the BCD using BootRec /RebuildBCD.
    4. Boot back into Windows on the Primary Disk.
    5. Delete the partitions from the Secondary Disk.
    6. Remove the old entry for the Secondary Disk from the BCD using BCDEdit.
    7. Remirror the Primary back onto the Secondary (System Reserved and Windows OS partitions).
    • Marked as answer by jdz.tsg Friday, April 28, 2017 12:34 PM
    Friday, April 28, 2017 12:34 PM