Our suggestion is to allow a clustered instance of SSAS to access a local physical disk (perhaps SSD) instead of shared disk allocated in the cluster.
We will maintain the sync of the cube files on the local disk manually.
In our environment, shared disk (SAN) is an expensive option, especially for the read IO that would benefit a cube. Our cubes are built in another environment and copied to the read environment for general access.
The benefit of local disk from the clustered instance gives us the benefit of cluster while allowing us flexibility in the storage section.