‘Add Mirror…’ option is grayed out in Windows’ Disk Management

How to ‘Add Mirror’ on a disk containing data when the option is grayed-out although you have another very similar disk available and empty? Check that your two disks are “Dynamic” and shrink the volume on the disk with data!

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I had a 2 TB disk with a unique volume (on one single partition), containing data.

I did add a new 2 TB disk to be used as a mirror of the existing one. I went into the Disk Management tool to “add Mirror” but found that this option was not available. The menu was disabled:

Add Mirror Grayed Out
Add Mirror Grayed Out

First thing to check: the two disks to be used must be “Dynamic”. Right-click on “Disk x” to “Convert to Dynamic Disk …”.

Next, to be able to create a mirror, the system needs some free space to create its own reserved partition on the disk. So, right-click on the Volume of the disk with data to “Shrink Volume…” (Try first with 1 Mb). Once the disk has been shrunk, the menu “Add Mirror…” becomes accessible.

Add Mirror Enabled
Add Mirror Enabled

Et voilà.

NB.:

  • It does not matter if the disks are MBR or GPT.
  • Once the volume shrunk, you will possibly have to reboot.
  • If you encounter an issue while adding a mirror, do a “Check Disk” (Properties > Tools > Check).
  • If you can really not get rid of the error “DiskPart has referenced an object which is not up-to-date.” although rebooting, do an “Extend Volume” of 1 MB! (Sound silly, I know…) and then “Add Mirror”.
  • In my case, while the disks were re-syncing, I did remove the mirror, did an “Extend Volume” to reuse the whole free space, and was still able to do an “Add Mirror”.
  • MS Partition & Volume Info here.

Mirror using DiskPart

  • Run DiskPart in a cmd prompt started as Administrator
  • list disk
  • select disk x [x=disk containing the volume to be mirrored]
  • list volume
  • select volume x [x=volume to be mirrored]
  • add disk x [x=disk to be used for mirroring]

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Comments

7 responses to “‘Add Mirror…’ option is grayed out in Windows’ Disk Management”

  1. ivan Avatar
    ivan

    very helpful fixed my issue

  2. amonrei Avatar
    amonrei

    5 years late but thanks. This works. I searched far and wide on the internets for this solution.

  3. clark Avatar
    clark

    you’re a lifesaver! THIS is the solution!

  4. Marc Kircos Avatar
    Marc Kircos

    Disk to Mirror is 1TB, tried to use a 2TB as the add disk for mirror and received this message: The specified disk extent size exceeds the size of free disk space. What do I try now?

    1. vletroye Avatar

      I didn’t experience such an error myself, so I can’t confirm that this solution found on Google will do the trick: “Taking the drive offline in Disk Management, rescanning disks, and placing the drive back online”.

  5. Max_fromOz Avatar
    Max_fromOz

    I had tried for hours and was getting nowhere, found the above method and when I deleted the volume and made the drive 100% unallocated then the ‘add mirror’ became a valid option…unfortunately I then got a new error telling me the drives had to be the same format (both drives are GPT, not MBR). At the time I got this error both drives were GPT so it didn’t make any sense. I changed the 2nd drive back to MBR (had it that way originally but had formatted it NTFS, so not unallocated) but got the same error. Changed 2nd drive back to GPT and voila!…suddenly worked fine. Makes no sense but it worked. So if you’re stuck try swapping drive back and forth between MBR and GPT.

    1. vletroye Avatar

      Interesting finding 🙂

      Thx for sharing !

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