A couple notes on my experience with distributed rendering in with After Effects, which may help you as you build out your render farm:
All the render nodes will need to have any plugins and fonts used in the project.
Different plugins carry different license restrictions for render nodes. Some allow only one install per license, some allow five or ten, and some are unlimited.
Multiple cores/processors count in the "maximum number of machines." If you have four quad-core render nodes, you need a maximum of at least 16 (and probably more with hyperthreading).
I never recommend OpenGL rendering, but it's especially important not to use it here; different graphics cards could render the same effect differently on neighboring frames.
AE's network renderer is somewhat naive. Each node gets the same sequence, and looks to the shared storage to see what frames have been rendered already, and will take the first unrendered frame in the range. As you add render nodes, you greatly increase load on you network and on the shared disk subsystem. A fast network and a beefy file server are very important. Without that, it may be faster to manually split your render across your multiple workstations.
AE's network render always works with image sequences. If any you need to make any tweaks, you only need to delete the image files representing the affected frame range and re-render. The network render will only re-render the missing frames.
You can use the "set proxy" post-render action to automate conversion from the image sequence to a movie file. In "Output Module" for the comp, set the post-render action to "Set proxy." Add the comp to the render queue a second time and choose whatever output settings you require. Under "Render Settings" change "Proxy Use" to "Use All Proxies." Once the multi-machine image sequence has been created, one of the nodes in your network will go through the image sequence and create your movie file. Again—a fast network and disk subsystem are a must.
Walter Soyka, Principal
Keen Live, Inc.
Presentation, Motion Graphics & Widescreen Design
RenderBreak: A Blog on Innovation in Production
