1. A method, comprising: generating a first instance of a deployment descriptor and sending said first instance of said deployment descriptor to a first computing system, said first instance of said deployment descriptor specifying a persistence scope that does not extend beyond said first computing system, said first computing system having multiple virtual machines, said first computing system not having shared memory accessible to each of said virtual machines for storing persisted session information; and, generating a second instance of said deployment descriptor and sending said second instance of said deployment descriptor to a second computing system, said second instance of said deployment descriptor specifying a persistence scope that does not extend beyond said second computing system, said second computing system having multiple virtual machines, said second computing system having shared memory accessible to each of said second system's virtual machines for storing persisted session information; as a consequence of said first computing system receiving said first instance of said deployment descriptor, persisting a first session's session state information in said first computing system's file system; and, as a consequence of said second computing system receiving said second instance of said deployment descriptor, persisting a second session's session state information in said second computing system's shared memory.