Software mirrored boot volumes in Windows Server 2008 cannot be broken from Disk Management

Source: Microsoft Support

RAPID PUBLISHING ARTICLES PROVIDE INFORMATION DIRECTLY FROM WITHIN THE MICROSOFT SUPPORT ORGANIZATION. THE INFORMATION CONTAINED HEREIN IS CREATED IN RESPONSE TO EMERGING OR UNIQUE TOPICS, OR IS INTENDED SUPPLEMENT OTHER KNOWLEDGE BASE INFORMATION.

Consider the following scenario.� You have a system running Windows Server 2008, and this system has two Dynamic Disks containing a volume that is being software mirrored by Windows.� You open Disk Management and try to break the mirror of the boot volume.� Disk Management prevents you from breaking the mirror of the boot volume with the following error message:

The specified plex is a the current system or boot plex. [sic]

This behavior is by design.� However, the mirror can be broken using DiskPart.exe as described in the "Resolution" section.

The boot mirror can be broken from DiskPart.exe using the following steps:

1. From an elevated Command Prompt, type diskpart�to start DiskPart.
2. Use the list volume command in DiskPart to list the volumes present on the system.
3. Type�the command�select volume x to select the mirror volume, where x is the alphanumeric identifier of the mirror volume.
4. Determine the numeric identifier of the disk containing the plex you are currently booted into ("Boot Disk") using the list disk, select disk,�and detail disk commands.
5. Use the command break disk=n� to break the mirror, where n�is the numeric identifier of the disk containing the mirror plex you are not currently booted from.
6. The mirror will be broken, and both plexes will be converted to Simple volumes.

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