If you put Apache server in front of your Tomcat servers, you can use mod_jk's load-balancing capabilities or mod_proxy.
For load balancing in Tomcat, see below:
Tomcat 5.0.15 and later ships with a webapp named balancer. This is a simple implemention of a rules-based load balancer. It was not designed as a replacement for other load-balancing mechanisms used for high traffic environments. Rather, it is a simple, pure Java, easily extensible, and fast way to direct traffic among multiple servers.
Although balancer ships with Tomcat, it is not Tomcat-specific and runs on other containers without any modification. The balancer webapp requires a Servlet Specification 2.3 or later container if you wish to use a filter to redirect traffic. If you wish to redirect traffic using a servlet, you may use any servlet container.
[ March 03, 2005: Message edited by: Surasak Leenapongpanit ]