Network Programming in .NET

If you want to break a mirrored volume in Disk Management, because you want to resize the partition where your If you want to break a mirrored volume in Disk Management, because you want to resize the partition where your operating system is installed, then you may get the following error:

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

As per KB 969749, the solution is detailed as follows, I’ve just added the commands required.
From an elevated Command Prompt, type diskpart to start DiskPart.

C:\Windows\system32>diskpart
Microsoft DiskPart version 10.0.14393.0
Copyright (C) 1999-2013 Microsoft Corporation.
On computer: xxxxxx

Use the list volume command in DiskPart to list the volumes present on the system.

DISKPART> list volume
Volume ###  Ltr  Label        Fs     Type        Size     Status     Info
———-  —  ———–  —–  ———-  ——-  ———  ——–
Volume 0     X   xxxx     NTFS   Spanned     xxxx MB  Healthy
Volume 1     X   xxxxx        NTFS   Mirror       xxx GB  Healthy    Boot
Volume 2         EFI          FAT32  Partition    xxx MB  Healthy    System
Volume 3         EFI          FAT32  Partition    xxx MB  Healthy    Hidden

Type the command select volume x to select the mirror volume, where x is the alphanumeric identifier of the mirror volume.

DISKPART> select volume 1
Volume 1 is the selected volume.

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.

DISKPART> list disk
Disk ###  Status         Size     Free     Dyn  Gpt
——–  ————-  ——-  ——-  —  —
Disk 0    Online          xxx GB  1024 KB   *    *
Disk 1    Online          xxx GB  1024 KB   *    *

DISKPART> select disk 0

Disk 0 is now the selected disk.

DISKPART> detail disk
INTEL xxxxx
Disk ID: {xxxx}
Type   : xxxx
Status : OnlinePath   : 0
Target : 0LUN ID : 0
Location Path : …..
Current Read-only State : No
Read-only  : No
Boot Disk  : Yes
….
DISKPART> select disk 1
Disk 1 is now the selected disk.
DISKPART> detail disk
INTEL xxxxx
Disk ID: {xxxxx}
Type   : xxxx
Status : Online
Path   : 0
Target : 0
LUN ID : 0
Location Path : …
Current Read-only State : No
Read-only  : No
Boot Disk  : No
Pagefile Disk  : Yes
Hibernation File Disk  : No
Crashdump Disk  : Yes
Clustered Disk  : No
….

If you try to break the disk without selecting the volume, then you get the following error:

DISKPART> break disk 1
There is no volume selected to break.Please select a dynamic mirror to break.

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.The mirror will be broken, and both plexes will be converted to Simple volumes.

DISKPART> select volume 1
Volume 1 is the selected volume.
DISKPART> break disk 1
DiskPart successfully broke the mirror volume.

After this is done, you will have two simple volumes, rather than one mirrored volume which will be very similar in content. You can then use Disk Management to resize, the volumes, dealocate one of them, then select the boot volume and press Add Mirror to restore the Raid.