I assume your RAID controller supports expanding the RAID set and the logical volume!?
If the VMFS datastore is located on the boot drive, you can't resize it from the vSphere Client GUI, but need to resize it from the command line (see http://kb.vmware.com/kb/2002461) Please make sure you have a backup of the VMs in case something doesn't work as expected.
Also keep in mind that with some RAID controllers volume sizes of >2TB are not supported (see e.g. http://kb.vmware.com/kb/2006942)
Welcome to the communities.
Is there nay error while extending the storage.
Please follow below KB to resolve this ./p>