This backend uses the PHP memcached module to communicate with a memcached server. It is pretty fast and allows for some basic "clustering" (that isn't really clustering but thats what the memcached guys call it). It's really just "not-so-fancy" partitioning.
server - The memcached server to connect to, or an array of servers. Default: localhost.
port - The port to connect to the server on. Default: 11211
use_compression - Enables compression on the communication link. Default: false