SAN  You can provide SAN access to CLARiiON LUNS within a single CLARiiON Raid Group (4 + 1).  In your case (2), one for the Celerra and one for VMware.  NAS  You can also use the same Celerra Storage Pool for different file systems, for CIFS.NFS access and/or iSCSI targets.  VMware would access Celerra storage via the network from one of these protocols.   Note for Celerra Control LUNS  In any case, best practices say that the Celerra Control LUNS are usually bound to a Raid Group that will have only Celerra bound data LUNS and not data LUNS for other hosts.
If we use one lun in a storage pool (disk group) for cifs storage, does that mean that any other luns in that storage pool must also be used for cifs storage and are not available for other uses? 
Cifs storage allocation