Assuming you have the following cluster config...  HostA has boot LUN10 HostB has boot LUN11 SQL DB on LUN20 SQL Log on LUN21  Storagegroup "hosta"      LUN10 = HLU0      LUN20 = HLU1      LUN21 = HLU2  Storagegroup "hostb"      LUN11 = HLU0      LUN20 = HLU1      LUN21 = HLU2  With these two storage groups, each host only sees it's own boot LUN but both hosts see the same DB and Log LUNs, and because the two SQL LUNs have the same HLU# in each storage group, they will operate properly in the cluster.
What is the rule of thumb when creating storage groups?  How do I know when I should add more storage groups to my infrastructure? 
Creating Storage Groups