Apache Java server
Note this tutorial sets up two seperate solr applications in tomcat, not multi core in one java application.
ApacheSolr for Drupal 6 improves on the out-of-the-box search experience for Drupal users. The easiest way to get Solr running on your Drupal web site is to use the hosted service provided by Acquia; it is way easier than running your own Solr. You simply point your queries to their Solr server and you’re done.