Manual:$wgMainCacheType

Details
Object cache setting. Replaces $wgUseMemCached.

Here are the available CACHE constants, as defined in Defines.php


 * CACHE_ANYTHING - Use anything, as long as it works
 * CACHE_NONE - Do not cache
 * CACHE_DB - Store cache objects in the DB
 * CACHE_MEMCACHED - memcached, must specify servers in $wgMemCachedServers
 * CACHE_ACCEL - APC --> XCache (--> WinCache, if on Windows), trying each in this order, using whichever is available


 * CACHE_DBA - Use PHP's DBA extension to store in a DBM-style database in $wgTmpDirectory with $wgDBAhandler


 * Roan Kattouw has stated that CACHE_MEMCACHED directive will provide the most significant performance improvements in the case where you have memcached and an opcode cache installed. APC still caches ( others may as well,) though I am unsure it is used in the final transaction with the client.
 * This is just one of MediaWiki's caching settings. For best performance you may need to consider other caching settings, such as $wgParserCacheType. See also Squid or Varnish which can help a lot.