Day to day
Choosing a cache backend
Where cached pages are stored is interchangeable; the module automatically falls back to an available engine if the configured one isn't supported on the server.
Filesystem (default)
One file per cached page. Works everywhere, no special dependency.
Zip
Same files, compressed on the fly: less disk space, useful on constrained hosting.
Memcached
In-memory cache, the fastest of the three. Requires a Memcached server reachable from PHP.