* Store::MultiFile
    - hierarchal directory structure
    - filesystem based delete_expired_sessions
    - no locking (update?)
    - NFS friendly
* Store::BerkeleyDB
    - complement FastMmap, but no LRU silliness
* Catalyst::Plugin::Semaphores
    - possible drivers
        - memcached
        - flock
        - berkeleydb
        - fastmmap