We want to set up a test cluster for Exchange Server. Does our cluster hardware absolutely need to be on the Microsoft Hardware Compatibility List (HCL)?
In a word, yes. The HCL, which is available at http://www.microsoft.com/hwdq/hcl, lists combinations of computers and storage equipment that Microsoft has certified as working together. If you encounter a clustering problem and call Microsoft Product Support Services (PSS), they have no immediate way to tell what's causing the problem: It might be broken hardware, but it could also be a subtle interaction between two components that haven't been tested for proper function in clustered environments. You might be able to get away with non-HCL components in a test cluster, but to avoid future problems, stick with the HCL when you purchase hardware for your production cluster.