Many modern disk arrays allow existing LUNs to be resized. Veritas Volume Manager (VxVM) supports dynamic LUN expansion, by providing the Rescan utility.

Resizing should only be performed on LUNs that preserve data. Consult the array documentation to verify that data preservation is supported and has been qualified. The operation should be performed on the host where the disk group is imported (or on the master node for a cluster-shared disk group).

When a disk is resized from the array side, you must perform the Rescan operation from the VxVM side to make VxVM aware of the new size. After the Rescan operation the volumes on the device should be grown.

Before shrinking a LUN, first shrink any volumes on the LUN or move those volumes off of the LUN. Finally, resize the LUN itself using the storage array's management utilities.