Of course, it really depends on the size of the server. ~80% of in-house usage comes from requesting known package (id+version), so this is a fairly performant operation and doesn't take much searching. So, one or two servers is usually ok. For very large package stores (100k+), we seem to have hit some interesting file system / FileWatcher limitations; it works, but sometimes the indexer just stops working. We do plan to redesign the package store, but the work around is easy (just restart the indexing service) Please see http://inedo.com/support/kb/1073/load-balanced-and-high-availability-installation-of-proget for more information on LA/HA proget.

As for the architecture, BuildMaster consists of four main deployable components: Web Application - the primary interface to BuildMaster Service - running aside the web application, the BuildMaster Service is a Windows Service that performs tasks requested through the Web Application Database - a SQL Server database which stores the state and history (you can use your own if you have one) Agent - a light-weight application installed on servers in which BuildMaster can manage and orchestrate Hope that helps.