MediaWiki:Config-mysql-myisam-dep/en

Warning: You have selected MyISAM as storage engine for MySQL, which is not recommended for use with MediaWiki, because:
 * it barely supports concurrency due to table locking
 * it is more prone to corruption than other engines
 * the MediaWiki codebase does not always handle MyISAM as it should

If your MySQL installation supports InnoDB, it is highly recommended that you choose that instead. If your MySQL installation does not support InnoDB, maybe it's time for an upgrade.