...
Finally, if you're willing to give up some features and (in many cases) do some custom development, it's possible to deploy the IdP in a configuration that does not rely on shared runtime state. See this topic for more information.
Proxy Clustering
Further finally, if you front-end your server with Apache and are willing to give up some features, it's possible to cluster an IdP using Apache rewrite and proxy directives . See this topic for more information.