In 2005 I saw a demo of this product from VirtualIron called VFe, which did this on a smaller scale (maybe 10 servers) -- it looked amazing.
https://www.kernel.org/doc/ols/2005/ols2005v2-pages-243-258....
https://www.kernel.org/doc/ols/2005/ols2005v2-pages-243-258....