The SnapInfo LUN must be a Cluster disk:
When you create a LUN using Snapdrive (Launch from the Cluster Ressource), the LUN can be either "Shared" or "dedicated", for the SnapInfo, select "Shared (Microsoft Cluster Service Only)"
Then you will be asked to map the LUN to all nodes of the cluster, which you cannot do with a standard LUN.
In the pane "Microsoft Cluster Service Group" just select either an existing group name (cluster group or Available storage) or create a new group "Snapinfo Group".
But don't select : "Add to cluster shared Volume" => The SnapInfo path must not reside on a CSV.
The snapinfo LUN will appear in your cluster disks list in the group you selected.