‘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.


  • 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]




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

  1. ivan Avatar

    very helpful fixed my issue

  2. amonrei Avatar

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

  3. clark Avatar

    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”.

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