Memcached provides a custom session handler that can be used to store user sessions in memcache. A completely separate memcached instance is used for that internally, so you can use a different server pool if necessary. The session keys are stored under the prefix memc.sess.key., so be aware of this if you use the same server pool for sessions and generic caching.
Set to memcached to enable sessions support.
Defines a comma separated of hostname:port entries to use for session server pool, for example "sess1:11211, sess2:11211".