Cluster & gfs2

Hi all,

(my question is related more to design of the cluster: which component if the cluster is required and which not).

I am going to use gfs2 on two node cluster. The switch over will be carried out at the application level not the cluster
(so the main component we need is the clustered filesystem on shared LUN).
Is clustered LVM needed to do so ? Or can I put gfs2 directly on shared LUN and just use it ?