Today I have created a new datastore in a new volime using the VSC with a size of 100GB, VSC is configured to create the volume 20GB bigger than the datastore.
I have then tried to increase the size of this datastore using the VSC and still get the error above. I can increase the size of the volume using System Manager and then increase the size of the LUN (again in System Manager) and then increase the size of the datastore. But I should be able to do all of this with VSC by just specifying the new datastore size and let it resize the volume, LIN and finially the datastore for me.
I have done the same by trying to resize a datastore with VSC and when it fails with the message in my original post on this subject I can increase the volume and LUN at the command line and then increase the datastore with teh vSphere Client.