Error Message When You Use the DiskPart Break Command to Break a Mirrored Set


Symptoms


When you use the DiskPart text-mode command interpreter (Diskpart.exe) and you select a mirrored volume and then use the break command to break the mirrored volume in two volumes, you may receive one of the following error messages:
The arguments you specified for this command are not valid.
-or-
The disk management services could not complete the operation.

Cause


This behavior may occur if one of the two disks that contain the mirrors is missing and you are using incorrect syntax for the break command.

Resolution


To resolve this behavior, use the disk parameter to refer to the missing disk, and use the nokeep parameter.

Without the nokeep parameter, the break command tries to convert both mirrors to simple volumes, retaining the data. If one of the disks is missing, this is not possible. By using the nokeep parameter, you retain only one half of the mirror as a simple volume, and the other half is deleted and converted to free space. Neither volume receives the focus.

For example, select the mirrored volume, issue the "detail volume" command, then break the mirror as follows:
diskpart> List Volume

Volume ### Ltr Label Fs Type Size Status Info
---------- --- ----------- ----- ---------- ------- --------- --------
Volume 0 D data_vol NTFS Mirror 737 KB Failed Rd
Volume 1 C system NTFS Simple 3000 MB Boot

diskpart> select volume 0

Volume 0 is the selected volume.

Diskpart> detail volume

Disk ### Status Size Free Dyn Gpt
---------- ------- ------- --- --- ---
Disk 1 Online 1023 MB 737 KB *
Disk M0 Missing 1022 MB 0 B *
In this example, the correct command to break the mirrored volume is:
Diskpart> break disk=m0 nokeep
After you issue this command, the mirror on Disk 1 is converted to a simple volume, and the reference to the missing mirror is deleted from the Logical Disk Management (LDM) database.

Status


This behavior is by design.

More Information


For additional information about using DiskPart to manage disks, click the following article number to view the article in the Microsoft Knowledge Base:
300415 A Description of the DiskPart Command-Line Utility