I have VNX5300 under VPLEX.  My VPLEX is running 5.1.3.  One of my LUNs is 500GB and we are going to expand it to 800GB.  It is pretty easy to do it without VPLEX.  We can just expand the LUN under VNX and rescan on the windows host.  Now it seem like under VPLEX, even LUN has increase 800GB the size was not recognized.