$db['default'] = array(
        'dsn'   => '',
        'hostname' => 'localhost',
        'username' => 'root',
        'password' => '',
        'database' => 'database_name',
        'dbdriver' => 'mysqli',
        'dbprefix' => '',
        'pconnect' => TRUE,
        'db_debug' => TRUE,
        'cache_on' => FALSE,
        'cachedir' => '',
        'char_set' => 'utf8',
        'dbcollat' => 'utf8_general_ci',
        'swap_pre' => '',
        'encrypt' => FALSE,
        'compress' => FALSE,
        'stricton' => FALSE,
        'failover' => array(
            array(
                    'hostname' => 'localhost1',
                    'username' => '',
                    'password' => '',
                    'database' => '',
                    'dbdriver' => 'mysqli',
                    'dbprefix' => '',
                    'pconnect' => TRUE,
                    'db_debug' => TRUE,
                    'cache_on' => FALSE,
                    'cachedir' => '',
                    'char_set' => 'utf8',
                    'dbcollat' => 'utf8_general_ci',
                    'swap_pre' => '',
                    'encrypt' => FALSE,
                    'compress' => FALSE,
                    'stricton' => FALSE
            ),
            array(
                    'hostname' => 'localhost2',
                    'username' => '',
                    'password' => '',
                    'database' => '',
                    'dbdriver' => 'mysqli',
                    'dbprefix' => '',
                    'pconnect' => TRUE,
                    'db_debug' => TRUE,
                    'cache_on' => FALSE,
                    'cachedir' => '',
                    'char_set' => 'utf8',
                    'dbcollat' => 'utf8_general_ci',
                    'swap_pre' => '',
                    'encrypt' => FALSE,
                    'compress' => FALSE,
                    'stricton' => FALSE
            )
        )
);