Reactivate a Missing or Offline Dynamic Disk

Applies To: Windows 7, Windows Server 2008 R2

A dynamic disk may become Missing when it is corrupted, powered down, or disconnected.

A dynamic disk may become Offline if it is corrupted or intermittently unavailable. A dynamic disk may also become Offline if you attempt to import a foreign (dynamic) disk and the import fails. An error icon appears on the Offline disk. Only dynamic disks display the Missing or Offline status.

Only dynamic disks can be reactivated.

BackupOperator or Administrator is the minimum membership required to perform these steps.

Reactivating a missing or offline dynamic disk

  • Using the Windows interface

  • Using a command line

To reactivate a dynamic disk by using the Windows interface

  1. In Disk Management, right-click the disk marked Missing or Offline.

  2. Click Reactivate Disk. The disk should be marked Online after the disk is reactivated.

To reactivate a dynamic disk by using a command line

  1. Open a command prompt and type diskpart.

  2. At the DISKPART prompt, type list disk. Make note of the disk number of the missing or offline disk that you want to bring online. Missing disks are numbered M0, M1, M2, and so on, and offline disks are numbered 0, 1, 2, and so on.

  3. At the DISKPART prompt, type select disk <disknumber>.

  4. At the DISKPART prompt, type online.

Value Description

list disk

Displays a list of disks and information about them, such as their size, amount of available free space, whether the disk is a basic or dynamic disk, and whether the disk uses the master boot record (MBR) or GUID partition table (GPT) partition style. The disk marked with an asterisk (*) has focus.

select diskdisknumber

Sets the focus to the specified disk, where disknumber is the disk number.


Brings an offline disk or volume with focus online.

Additional references