synchronize Cache between two transparent proxy server

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http://www.linuxforums.org – i would like to setup two transparent proxy server that use Ubuntu Server and Squid as transparent proxy. My idea is to synchronize the cache between Proxy 1 and proxy 2. so both Proxy server will have same cache inside them. I wish to use Rsync that is an open source utility that provides fast incremental file transfer. It is possible?between the proxy, if both proxy run at the same time or only one will run at one time?.it will have a firewall that is pfSense that will redirect traffic to each proxy server. ..can someone show me how the configuration..since i new to this p/s embeded link is (HowTos)