We are implementing Umbraco to an existing site that is hosted on several load balanced web servers.  The issue we have is that we cannot access each individual web server by IP or hostname, trust me when I say the customer is adamant this cannot be changed.  Because of this restriction we are unable to use Umbraco's built in cache refreshing feature via the distributedCall setting. 

We have configured the web servers to use an umbraco.config file stored centrally on a SAN, the question is where is the data stored in memory?  If we know where this is stored we will consider implementing a shared caching solution that we can refresh.