Apache+Tomcat集群，Tomcat Cluster的Session复制问题

Apache: 10.1.2.3
tomcat server1:10.1.2.2
┠─Tomcat1------worker1
┠─Tomcat2------worker2
┠─Tomcat3------worker3

tomcat server1:10.1.2.8
┠─Tomcat4------worker4
┠─Tomcat5------worker5
┠─Tomcat6------worker6

Apache:
apache/conf/extra：httpd-vhosts.conf,如下

ServerAdmin xxyujian@gmail.com
ServerName xxx.xxx.com
ServerAlias xxx.xxx.com
ProxyRequests Off

BalancerMember ajp://10.1.2.2:8009 loadfactor=1 route=worker1
BalancerMember ajp://10.1.2.2:8109 loadfactor=1 route=worker2
BalancerMember ajp://10.1.2.2:8209 loadfactor=1 route=worker3
BalancerMember ajp://10.1.2.8:8009 loadfactor=1 route=worker4
BalancerMember ajp://10.1.2.8:8109 loadfactor=1 route=worker5
BalancerMember ajp://10.1.2.8:8209 loadfactor=1 route=worker6

ProxyPass / balancer://cluster/ lbmethod=byrequests stickysession=JSESSIONID nofailover=Off timeout=5 maxattempts=3
ProxyPassReverse / balancer://cluster/
ErrorLog "logs/study.com-error_log"
CustomLog "logs/study.com-access_log" common

Tomcat：我原本是想tomcat1与4，tomcat2与5，tomcat3与6，组成三组子集群进行session复制，但是服务器之间session复制不了，后来我改用在同一台服务器上两个tomcat,如tomcat1与2,这样可以进行Session复制，即我访问程序，当前使用tomcat1,我手动停止tomcat1,再刷新页面或跳转到其它tomcat1的session会话被复制到tomcat2上进行。不知道可否在两台服务器上的tomcat之间进行Session复制，如何设置，我的tomcat的Server.xml配置如下：
#同一台服务器上端口不一样
#同一台服务器上AJP端口不一样
#jvmRoute，每一个tomcat取唯一值

channelSendOptions="8">
expireSessionsOnShutdown="false"
notifyListenersOnReplication="true"
mapSendOptions="8"/>



address="228.0.0.4" # 同一组tomcat集群一样
port="45564" # 同一组tomcat集群一样
frequency="500"
dropTime="3000"/>
address="auto"
port="4000" #同一个机器上端口不一样
autoBind="100"
selectorTimeout="5000"
maxThreads="6"/>









filter=""/>


tempDir="/tmp/war-temp/"
deployDir="/tmp/war-deploy/"
watchDir="/tmp/war-listen/"
watchEnabled="false"/>