Manual:External Storage

From MediaWiki.org

External storage stores page text on a separate DB server to the main wiki database.

[edit] How to set it up

• Create the database. In most cases you want to give it the same name, username and password as the wiki's main database (other usernames and passwords are supported by using an LBFactory_Multi
• Source maintenance/blobs.sql using php maintenance/sql.php maintenance/blobs.sql.
• Configure it locally, add to LocalSettings.php:

$wgExternalStores = array('DB');
$wgExternalServers = array( 'cluster1' => array( 'master-server', 'slave-1', 'slave-2' ) );
$wgDefaultExternalStore = 'DB://cluster1';