When you create or remove LUNs on a storage system, the managed disk (MDisk) view is not automatically updated.
You must issue the svctask detectmdisk command-line interface (CLI) command or use the Discover MDisks function from the SAN Volume Controller Console to have the cluster rescan the fibre-channel network. The rescan discovers any new MDisks that might have been added to the cluster and rebalances MDisk access across the available controller device ports.