Hey Peter,
Before starting on any renderfarm design, it is a good idea to figure out what you plan to use it for. In your case, high end photo real work. This can be different from studio to studio as different kinds of CG work have very different resource requirements. For example, texture sizes for high end CG work do tend to be higher in quality and size. You also normally render at a higher resolution and probably require more time per frame on average. In the case where you don't have a large staff, it is a good idea to think about consulting work for the design of your farm since network and storage equipment in higher end farms as well as cooling requirements can be vastly different between the home grown 10-20 machine farm versus the industrial farms you find in film work which can be 1000's of machines strong.
Before choosing the kind of farm machines you will use, the Operating System and Hardware are typically the biggest factors in your choice. If you plan on using 3d Studio Max for instance, then you can only use Windows workers. If you plan on using Maya then your best bet is Linux (at least for the farm) In our experience however, the best platform to choose is normally the one you use for your desktop machines. This is to keep everything homogeneous. It simplifies maintenance since you do not have to learn 2 different operating systems and their interoperability.
For a well designed render farm, you need these components at minimum:
Network backbone hardware (Switches, Routers, etc...)
Ex. Cisco, Foundry and HP...
Network File Storage
Ex. NetApp, Microsoft File Server...
User Management Server
Ex. Microsoft Primary Domain Controller (Windows)
Ex. NIS (Unix/Linux)
Ex. OpenLDAP (Apple/Linux/Unix)
Farm Management Server
Ex. Qube!
For a render farm of around 50 machines, you'll need to think about these things:
How much physical space do I have?
Is the room ready for the hardware?
Do I have enough cooling? Air-con
Do I have the power and breakers?
Do I need to worry about noise?
For many of these questions, it's best to talk to a vendor to get quotes on everything. They can spec out information such as how much airconditioning you'll need with the consideration of farm growth. How much power must go into the room, etc...
Please contact our sales department. We've actually setup several render farms for our clients and are more than willing to get you the resources close to your area to spec out the farm you "need" and will "grow" with you.
Thanks,
Anthony