If
Your comment is true, but only IF you have "a bunch" of ESX servers, AND you don't already have them running at 90% capacity.
Conversly, I am quite fond of running a pair of Hyper-V servers in a failover cluster with an iSCSI SAN. This setup minimizes the risk of down-time, and provides good performance for any applications that are not so heavily disk-bound that iSCSI doesn't provide the performance required.
Would I put my main firewall on it? NO!
Despite the expected segregation between VMs, I wouldn't care to trust anything except separtate physical hardware for something as critical as a firewall.
And there are few things as disk-intensive as an LOB database, so I would want to take a VERY careful look at the usage statistics before I virtuallized it.
