"You can use memcached over a network (i.e., install your web application on one server and memcached on another server), but usually you install both on one server to avoid the networking overhead.
It should be noted the memcached is no out-of-the-box solution for speeding up your web applications. Typically you have to adjust your scripts (PHP, Perl, etc.) to work with memcached, so this requires a little bit of work."
