Our organization is load testing our application using virtual servers via Hyper-V to see what the user load can be using fair equipment on a single box setup.

The developer group questioned the validity of the tests given the normal use of the box by the other virtual machines. IT admins answered that it is an acceptable platform to load test on because it has its own CPUs, memory and disks allocated.

Is their answer mostly correct? What hardware factors may be considered bottle necks given the other virtual machines when testing our application? For example, would bus speed be a concern or network IO?

The application consists of a windows service written using the 4.0 .NET Framework and SQL Server 2008 R2.