Repairing a Mirrored System Volume

When you mirror a system volume, an entry that allows you to boot to the secondary mirror is added to the system's boot configuration data. So, if a system fails to boot to the primary system volume, restart the system, and select the Boot Mirror - Secondary Plex option for the operating system you want to start. The system should start up normally. After you successfully boot the system to the secondary drive, you can schedule the maintenance necessary to rebuild the mirror if desired.

Rebuilding Mirrored System Volumes on MBR Disks

To rebuild the mirror, you must complete the following steps:

1. Shut down the system and replace the failed drive, and then restart the system using the secondary drive.
2. In Disk Management, right-click the remaining volume in the mirrored set, and choose Break Mirrored Volume. Click Yes at the prompts to confirm the action.
3. Next, right-click the volume again, and choose Add Mirror. Use the Add Mirror dialog box to select the second disk to use for the mirror, and then click Add Mirror.

If you want the primary mirror to be on the drive you added or replaced, perform these additional steps:

1. Use Disk Management to break the mirrored set again.
2. Make sure that the primary drive in the original mirror set has the drive letter that was previously assigned to the complete mirror. If it doesn't, assign the appropriate drive letter.
3. Right-click the original system volume, select Add Mirror, and then re-create the mirror.

Rebuilding Mirrored System Volumes on GPT Disks

For GPT disks, rebuilding mirrored system volumes is a bit different. To rebuild the mirror, shut down the system and replace the failed drive, and then restart the system using the secondary drive. In Disk Management, right-click the remaining volume in the mirrored set, and choose Break Mirrored Volume. Click Yes at the prompts to confirm the action. After this, you can use the secondary boot disk as your primary boot disk.