Could you please provide more details about these datastores which are part of SAN? Do you use them in same vCenter 5 with other datastores? Maybe you have them in some other vSphere version, in vSphere 4 there is no such entity as a Datastore Cluster.
Also I'm afraid you will not see an information about clusters which are part of SAN infrastructure, our MP collects only information about DS clusters which are created in vSphere, not about clusters in a low-level architecture of your SAN.
Hope this helps.