In the Expanding or growing a VMFS datastore recipe, we learned about how to increase the size of a datastore by utilizing the unused space on the same LUN backing the datastore.
You can run into a situation wherein there is no unused space on the LUN that is backing the VMFS volume, and the storage administrator is unable to expand the LUN any further. Fortunately, vSphere supports the spanning of a VMFS volume onto multiple LUNs. This means you can span the VMFS volume onto a new LUN so that it can use the free space on it. This process of spanning a VMFS volume onto another LUN is called extending a VMFS datastore.
