Increase volume size on Dell Compelent SAN to say 18TB.

ESX Server(s) see the increase after rescan.

As does vCenter.

However, when you try to increase the datastore that is mapped to this it either says there are no devices with free space:

Or on the local ESX machine it shows up, but only once after an increase and errors with this:

Dell looked at this on both the SAN side and the Dell Server side.  they think it's some kind of bug in the VMware (VMFS6) drivers.

Any ideas appreciated.