Redis cache config example

local.xml

        <!-- this is a child node of config/global -->
        <cache>
          <backend>Zend_Cache_Backend_Redis</backend>
          <backend_options>
            <server>127.0.0.1</server>
            <port>6379</port>
            <database>2</database>
            <use_redisent>0</use_redisent>  <!-- 0 for phpredis, 1 for redisent -->
            <automatic_cleaning_factor>20000</automatic_cleaning_factor> <!-- optional, 20000 is the default, 0 disables auto clean -->
          </backend_options>
        </cache>