Use a Ping node with UPS, Firewalls, Routers anything that is in the same subnets is also best and has high up time - see link below for more information. we spent allot of time on these video's that will help w/ some of your questions.

http://www.open-e.com/library/webcasts-and-videos/
2010.02 Open-E DSS V6 AutoFailover with VMware 4.0
2010.09 How to setup iSCSI Failover with Unicast Network connection mode