Using spanned volumes

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

Using spanned volumes

Spanned volumes combine areas of unallocated space from multiple disks into one logical volume, allowing you to more efficiently use all of the space and all drive letters on a multiple-disk system.

When you need to create a volume but do not have enough unallocated space for the volume on a single disk, you might be able to create a volume of sufficient size by combining sections of unallocated space from multiple disks into one spanned volume. The areas of unallocated space used to create spanned volumes can be different sizes. Spanned volumes are organized so that the space allocated to the volume on one disk gets filled up and then, starting at the next disk, the space allocated to the volume on that disk gets filled up.

Spanned volumes allow you to get more data on a disk without using mount points. By combining the space used by multiple disks into one spanned volume, you can free drive letters for other uses and enable the creation of a large volume for file system use.

Increasing the capacity of an existing volume is called extending. Existing spanned volumes formatted with the NTFS file system can be extended by the amount of unallocated space on all disks. However, after a spanned volume is extended, no portion of it can be deleted without deleting the entire spanned volume. Disk Management formats the new area without affecting any existing files on the original spanned volume. You cannot extend spanned volumes formatted with the FAT file system.

Before making any changes to spanned volumes, you should first back up all the information on the volume.

For procedures on working with spanned volumes, see Manage Spanned Volumes.


  • Spanned volumes cannot be mirrored and do not offer fault tolerance. If one of the disks containing a spanned volume fails, the entire volume fails and all the data on it is lost.

You can create spanned volumes on dynamic disks only. You need at least two dynamic disks to create a spanned volume. MS-DOS, Windows 95, Windows 98, Windows NT 4.0, Windows XP Home Edition, and other operating systems lacking dynamic storage capability cannot recognize any spanned volumes created by Windows 2000, Windows XP Professional, or Windows Server 2003 operating systems. Therefore, if you create a spanned volume on a dual-boot computer, the disks that make up that volume become unusable by those operating systems.