You may also want to look at Sanbolic Melio as a great alternative to Polyserve (now that Polyserve has been end-of-lifed). More info at http://www.sanbolic.com.
Sanbolic Melio has an App Cluster capability that is a great Polserve replacement (now that Polyserve has been EOL'd). More info at http://www.sanbolic.com