Expand the CLARiiON LUN on the ClaRiiON storage system to the desired LUN size, issue a rescan at the ESX level. Sometimes you have to rescan again before your metalun will be shown.(I have to find out why) Your old disk will disappear from storage adapter view and the new metalun wil be shown. [...]
To configure a proper highly available SAN failover configuration with EMC storage models equipped with two storage processors, each ESX Server must have: Two Fibre Channel host bus adapters (HBAs), such as QLogic or Emulex. Two fibre switches. Two storage processors (SPs): SPA and SPB. Each storage processor must have at least two ports connected [...]