Industrial Light & Magic's Offering for CG Rendering.
Nix only and as far as I have seen it will never be ported to Windows as there currently isn't a Windows System at a reasonable price capable of running it in the same time frame a a Nix Base.
I've seen this used with a 6K CPU Blade and it takes several days to render 30 seconds of Video the last estimate that I heard for a Windows system of compatible power was 3 weeks for the same thing.
The Licensing for SUSE which as used on that Blade is Zilch the Licensing for Windows is too Scary to Contemplate and the Support Costs are about the Same.
Which system would you chose if there was a version for each OS?

Col