How to create a Spanned Volume

A spanned volume is a volume that uses more than one physical disk. You can use any unallocated space left on disks to create a spanned volume. It also can include more than one unallocated space on a single disk while free spaces can be of any size. The only benefit of spanned volumes is the use of unallocated space that may have originated from imported disks or specific volume arrangements. The main disadvantage is the risk of losing the volume if one disk participating in the spanned volume fails. A faulty portion means a faulty spanned volume! There are no performance benefits when implementing spanned volumes.

To create a spanned volume, perform the following steps with administrator privileges:

  1. Open the Disk Management console by typing disk management in the Start search text box and click Create and format hard disk partitions or from the Computer Management console found in Control Panel\All Control Panel Items\Administrative Tools
  2. Convert disks to Dynamic if they are set as Basic, right-click a Disk (left-hand side) and select Convert to Dynamic – at a later stage, the wizard prompts you to convert disks if you skip this step
  3. From the Disk Management snap-in, select the empty disk to include in the spanned volume, right-click on the Unallocated space and select New Spanned Volume – the New Spanned Volume wizard starts
  4. On the Select Disks page, select and add the disks you want to include in the Spanned Volume. In the Selected: pane you can highlight a disk and specify the amount of disk space you want to use, then click Next
  5. Assign a Drive letter or path to the new spanned volume and format the volume – NTFS is the only option, to format with FAT or FAT32 use the Diskpart command line tool
  6. If all set parameters are correct, click Finish on the final Summary page

Creating a spanned volume with Diskpart requires some changes in the procedure. You start by converting disks to Dynamic, then creating a simple volume on the first disk of the spanned volume and finally extending it to the second and/or any additional disks. With Diskpart you can create a spanned volume on a basic disk using the free space on the same disk, if any! Basically, this is an extend operation of the existing volume. The same operation can be performed to extend simple or spanned volumes on dynamic disks. Remember, to specify the [size=<n>] parameter with the extend command if you wish to use part of the unallocated space, otherwise, all free space is used.