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  1. Dave
    March 31, 2021 @ 3:42 pm

    This is awesome, and I'm trial-running on a non-production set-up before I do it on a production PC. The instructions look perfect for the production PC, but on the trial set-up, clean install of UEFI Win10 Pro 20H2 loaded on to a 120GB SSD and I have the partitions in the order EFI, MSR, System, recovery, and not recovery, EFI, MSR, System. Has anyone experienced this, is it caused by the newer install media, or the size of the SSD. And if so, how have they adapted the instructions to fit this different configuration. I've tried, but I suspect converting to dynamic and mirroring the System drive should be the very last step, and since it isn't the last partition, is making the instructions difficult to transform to the slightly different configuration.


    • lakonst
      April 1, 2021 @ 11:51 am

      If your Recovery Partition has a different Partition Number than the one in the article (Partition 1), then change it accordingly at the "Mirror Recovery Partition" step. (At your case, type "select partition 4")


  2. Dave
    March 31, 2021 @ 2:17 pm

    So pleased these instructions exists, and I'm working through them, but I'm curious, for your uEFI instructions, how did the HD have the partitions in the order Recovery, System (UEFI), Reserved and Primary, when a clean load of Windows 10, for me, creates them in the order System (UEFI), Reserved, Primary, recovery. And does it make any difference to me as I complete the process.


    • lakonst
      April 1, 2021 @ 11:46 am

      Yes, it makes a difference. At your case you have to type the recovery Partition (or Volume) Number in the corresponding command: e.g. "select partition 4"


  3. Jim
    March 11, 2021 @ 6:34 pm

    Awesome article! My boot drive I wish to mirror is protected with Bitlocker security, which I understand must disabled before cloning. Once successfully mirrored will I be able to re-enable Bitlocker on the drive?


  4. Brian
    January 27, 2021 @ 7:22 pm

    Thanks for posting this. I just followed this on a 2019 Server install it is working.
    Just wondering, after this is setup, it is wise to create a daily Scheduled Task to copy the recovery and the EFI System partitions from drive 0 to drive 1? Do Windows Updates change these?


  5. mcgyvah
    September 29, 2020 @ 11:20 am

    Thanks for the write up. big thumbs up. i have the same error message as CJ (below). my drives are same seagate 2tb ( yes I know should use different, but its what I have) what else could cause this error message?
    "All disks holding extents for a given volume must have the same sector size, and the sector size must be valid."


    • lakonst
      September 30, 2020 @ 9:46 am

      This issue occurs because you cannot mirror drives that DO NOT HAVE the SAME SECTOR SIZE. ("Bytes Per Sector" & "Bytes Per Physical Sector"). To find out the sector size for each of your drives, give the command "fsutil fsinfo ntfsinfo drive_letter:" (without quotes) for both drives. (e.g. "fsutil fsinfo ntfsinfo C:" & "fsutil fsinfo ntfsinfo D:" )
      Finally, see the values 'Bytes Per Sector' & 'Bytes Per Physical Sector' on each drive. If they are not the same with the values on the other drive, then the mirroring can not be done.


  6. Andy
    September 14, 2020 @ 8:56 pm

    Thanks for the great article. I was able to create the mirror. I would like to test if primary fails, the secondary can boot. How do I do that? I can't remove or break the mirror since the primary fails. Please advise? Thank you


  7. Jose
    June 19, 2020 @ 6:57 pm

    Thank you very much for the tutorial, is the second time I'm following it, first one was on Win7 without problem. This time is different , is a fresh Win10 and in the step to convert the system disk to dynamic I'm getting the error saying “The disk could not be converted to dynamic because security is enabled on one or more partitions”, I tried disabling boot security features on UEFI, updating drivers, updating OS but no luck.
    I'm considering start again in MBR mode with the risk of the 2Tb limit per parition I wanted to avoid.
    Will you be so kind to give a hint?


    • lakonst
      June 20, 2020 @ 8:49 am

      I think that the partition is protected with Bitlocker security, which must disabled before cloning.


      • Jose
        June 20, 2020 @ 6:12 pm

        Thanks for your quick answer
        Bitlocker encryption is not active, nor TPM
        Any other thoughts?
        I'm still stucked trying to mirror system disk
        I also tried to do a fresh installation on the second hard disk, even on first boot after windows 10 install, conversion to dynamic is impossible with the same message
        Also can't find documentation about partition security or how to disable it


        • lakonst
          June 22, 2020 @ 10:24 am

          If you have Intel Chipset with a RAID controller, try to the install the Intel Rapid Storage driver, restart your PC and try to convert to Dynamic again.


  8. Gerard
    December 9, 2019 @ 3:32 am

    This worked great, but I want to remove all the extra letters created in the process. I was able to remove the S and T using DISKPART > list volume > select volume # > remove letter=s.

    But the Q and R letters do not show up with list volume and I can't figure out how to get rid of them. They appear in Windows Explorer under This PC, but not in Disk Management. And right-clicking the 499 MB Recovery partitions only brings up Help in the context menu.

    Anyone know how to fix this?


    • Gerard
      December 9, 2019 @ 4:09 am

      Never mind I figured it out. For anyone else who runs into this just use DISKPART > select disk # > list partition > select partition # (the one that's the right size) > remove letter=q.

      It will work even though the letter isn't listed.


  9. Billy
    October 11, 2019 @ 12:13 pm

    excellent article.
    is there any reason to retain the drive letters for the recovery/efi partitions



    • lakonst
      October 11, 2019 @ 1:51 pm



  10. Radek Homola
    October 10, 2019 @ 10:06 am

    What to do if I have to Dynamic Reserved ad Reserved
    Part 2: How to Mirror the EFI System Partition on Windows 10
    DISKPART> select disk 0

    Disk 0 is now the selected disk.

    DISKPART> list partition

    Partition ### Type Size Offset
    ————- —————- ——- ——-
    Partition 1 Recovery 499 MB 1024 KB
    Partition 2 System 99 MB 500 MB
    Partition 3 Dynamic Reserved 1024 KB 599 MB
    Partition 4 Reserved 15 MB 600 MB
    Partition 5 Dynamic Data 465 GB 615 MB
    Partition 6 Dynamic Data 465 GB 465 GB


    • lakonst
      October 10, 2019 @ 12:40 pm

      Unfortunately, I do not understand what you have done to your system and you have these "dynamic" partitions.


      • Harald
        February 7, 2020 @ 9:37 am

        I think this partition originate from the convertion from basic to dynamic disks.
        in my system they appeared after i converted the disks to dynamic


  11. MPH
    September 13, 2019 @ 11:48 am

    Would this work on windows server 2012? I really want to mirror my boot drive as I am worried about losing all the work I put into getting it up and running.


    • lakonst
      September 13, 2019 @ 2:01 pm

      I believe, YES.


  12. Troels
    September 4, 2019 @ 10:05 pm

    This was really useful to me! I went to re-install a workstation for a client, and I installed two SSDs assuming that the motherboard had Intel's chipset/software RAID-1, but it did not. This article saved the day for me. Thanks a lot for taking the time to write it!


  13. Miles
    August 31, 2019 @ 5:55 pm

    I have a 2Tb C: hhd drive that I mirrored to another 2Tb drive in Win10 The boot sector of the mirrored drive failed. I want to remove that mirror in the c: drive so I can clone the operating system and data onto an SSD but cannot do so until I remove the mirrror. Which steps do I need to take to remove the mirror in the C: drive. The Win 10 steps creating the mirror were quite easy now I need to undo that process. This is the second hhd failure wthin two years and that is the reason for switching to the ssd boot/ storage approach.


    August 30, 2019 @ 8:24 pm

    i recently upgraded my 500GB HDD with a 500GB SSD drive as my MBR C drive
    Will I be able to apply the steps in section Case A above or will I have to get a second identical SSD drive as the mirror drive?


    • lakonst
      August 31, 2019 @ 9:09 am

      @ROMAN HARABURDA: I believe that you must get a second identical SSD disk to do the mirroring.


        September 1, 2019 @ 7:30 pm

        Would I precipitate any issues if i attempt this? In other words if i convert Disk 0 from basic to dynamic, can i convert it back to Basic if this process wont accept Disk 1 as the mirror?


  15. Owen Harris
    August 3, 2019 @ 6:28 am

    An excellent tutorial. Thank you. I hit a couple of speedbumps along the way that perhaps others will hit. I got an error message saying not enough space to convert to dynamic. This was solved by using diskpart to blow away the WIN10 RECOVERY partition taking up 450MB at the end of the disk. I tried just the volume but that wasn't enough. You have to get rid of the partition as well. I also hit the "you don't have permission to delete issue so I used the OVERRIDE parameter. The next weirdness so trying to get the right SSD to act as the boot volume (i had an EVO 850 and an EVO 860 and I wanted the 860 to be the boot drive before I added the mirrors. That was just trial and error rebooting and restarting till I got what i wanted. Then I found that somehow my pagefile was on another SATA drive not my C:/ drive (not as a result of this procedure – just something I noticed which actually explains some issues I was having which is why I went down this path in the first place) so i had to move the pagefile by going into systemadvancedproperties and manually setting where I wanted the pagefile. Then I followed the mirroring process and it worked like a charm. So thank you very much. Changing a C: drive made me extra nervous (26 years in IT will do that to you).


  16. CJ
    July 14, 2019 @ 6:17 am

    Hello! This is a really great walkthrough – thanks so much. I have a system running Windows 10 (build 1903) I am trying to duplicate drive data on. It had a 2.5" HDD, and today I cloned the drive onto an SSD. I switched the SSD to the boot drive, and planned to make the HDD a RAID1 copy. I've done this before on an older Windows 7 box with 3.5" spinners, and don't recall having difficulty. Yet tonight I've spent hours, trying to sort this out.

    I found your guide, and followed it verbatim. At the end, though the Disk Management screen shows everything between disk 0 (boot SSD) and disk 1 (HDD) being equal, when I try to create a mirror for C: to the unallocated space on disk 1, I get this error:

    "All disks holding extents for a given volume must have the same sector size, and the sector size must be valid."

    This is driving me mad. I noticed that the Reserved space for mine had an extra line, in disk 0: I have "dynamic reserved" as an additional entry, listed at 1024KB.
    Reserved is 107 MB.

    The first time through, I entered 107. When that didn't work, I used "clean" to start over, then entered "108" for the "create partition msr size=" step. Same result, same error.

    I'm pretty frustrated at this point. I'm almost positive this was pretty simple in Win7, but I seem to be having troubles here. Any advice? It would be very much appreciated!


    • lakonst
      July 14, 2019 @ 9:56 am

      @CJ: Unfortunately, YOU CANNOT mirror different drives. The drives must be the same in size and characteristics.


      • CJ
        July 14, 2019 @ 11:21 am

        They are the same size, both are 500GB. I thought it would still work if one was SSD and one wasn't, but I guess not. Well, plan B would be to use the HDD for an image backup. Thanks!


  17. Bryan
    July 8, 2019 @ 5:41 pm


    Thank you for this great tutorial. This also works with Windows Server 2012 R2?
    If i try to start system with Disk 0 Missing, it just don't boot. I don't get any errors. In Bios SETUP in SATA devices, my hard disk appears. When I try to enter the boot options, Windows Boot Manager does not appear, only with disk 0. :/


  18. Bostjan
    May 8, 2019 @ 11:50 pm

    Hi there.
    Nice tutorial.
    I have followed the instructions for installing OS2019 with UEFI and GPT disks, but there is a small problem at each reboot.
    Follow the instructions percisely step-by-step but each time the machine is rebooted we get a pop up for Windows Boot Manager offering me two choices:
    Windows Server and Windows Server – secondary plex.
    You must manually select one of the option each time after you reboot.
    How to avoid that manual selection?

    With best regards


    • lakonst
      May 9, 2019 @ 9:35 am

      @Bostjan: For my opinion this selection is useful in case where you couldn't boot from the first disk. But if you want to disable it, open Explorer. Right click on "This PC" and click "Properties". Click "Advanced System Settings". At "Startup and Recovery" click Settings and then uncheck the "Time to display list of operating systems" box or set a lower value in time.


  19. Heather
    April 25, 2019 @ 6:58 pm

    I have attempted to run this on two SATA SSDs on a Z370 chipset motherboard, with the storage controller set to AHCI (so no IRST).

    Once this is set, it appears the OS can no longer send TRIM commands to the drives, and the Optimize and defragment program marks the "optimize" to the mirrored system drive greyed out as "optimization not available". Before creation of the mirror and conversion to dynamic, TRIM is supported and runs on a single drive in the optimize and defragment program.

    Has anyone else seen similar behavior?


  20. Russell Bantin
    March 30, 2019 @ 10:28 pm

    I have a legacy system and followed A to mirror. When I selected the system partition I was confronted with he error "The boot configuration data of the system could not be updated. Use bcdedit.exe to update it manually."


  21. Alex
    March 21, 2019 @ 5:57 pm

    When i booted with one drive missingit told me the BCD file was missing


  22. Shawn
    February 10, 2019 @ 3:46 am

    Awesome tutorial on the UEFI (GBT) Boot Drive mirroring process. Worked first try!!! Not sure if this is an improvement over Server 2012 or just a better tutorial, but I agonized for days it seems trying to make the official Microsoft guide work for 2012. I won, but it left me scared lol.


  23. Sam
    February 7, 2019 @ 5:20 am

    This was an excellent article! Worked perfectly to build a new Server 2019 setup with mirrored SSD drives. Thank you! -Sam


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