A spanned volume is a dynamic volume that consists of disk space on more than one physical disk. If a simple volume is not a system volume or boot volume, you can extend across additional disks. If you extend a simple volume across multiple disks, it becomes a spanned volume.

You can extend a volume only if it does not have a file system or if it is formatted using the NTFS file system. You cannot extend volumes formatted using FAT or FAT32.

Backup Operator or Administrator is the minimum membership required to complete the actions below.

Extending a simple or spanned volume

To extend a simple or spanned volume using the Windows interface
  1. In Disk Management, right-click the simple or spanned volume you want to extend.

  2. Click Extend Volume.

  3. Follow the instructions on your screen.

To extend a simple or spanned volume using a command line
  1. Open a command prompt and type diskpart.

  2. At the DISKPART prompt, type list volume. Make note of the number of the simple volume you want to extend onto another disk.

  3. At the DISKPART prompt, type select volume <volumenumber>. This selects the simple volume volumenumber you want to extend onto another disk.

  4. At the DISKPART prompt, type list disk. Make note of the number of the disk that you want to extend the simple volume onto.

  5. At the DISKPART prompt, type extend [size=<size>] [disk=<disknumber>]. This extends the selected volume onto disk disknumber and makes the extension size=size megabytes (MB).

Value Description

list volume

Displays a list of basic and dynamic volumes on all disks.

select volume

Selects the specified volume, where volumenumber is the volume number, and gives it focus. If no volume is specified, the select command lists the current volume with focus. You can specify the volume by number, drive letter, or mount point path. On a basic disk, selecting a volume also gives the corresponding partition focus.

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.


Extends the volume with focus into next contiguous unallocated space. For basic volumes, the unallocated space must be on the same disk as, and must follow (be of higher sector offset than) the partition with focus. A dynamic simple or spanned volume can be extended to any empty space on any dynamic disk. Using this command, you can extend an existing volume into newly created space.

If the partition was previously formatted with the NTFS file system, the file system is automatically extended to occupy the larger partition. No data loss occurs. If the partition was previously formatted with any file system format other than NTFS, the command fails with no change to the partition.

You cannot extend the current system or boot partitions.

disk= disknumber

The dynamic disk on which to extend the volume. An amount of space equal to size=size is allocated on the disk. If no disk is specified, the volume is extended on the current disk.

size= size

The amount of space, in megabytes (MB), to add to the current partition. If you do not specify a size, the disk is extended to take up all of the next contiguous unallocated space.

Additional references