Varnish Cache, the caching engine that powers cachoids, is memory and disk IO sensitive. The second disk IO weakens, due to unpredictable programs, Varnish ceases to deliver the great performance we expect from it.
Varnish needs to run on a server whose memory and disk IOPS do not fluctuate and deviate significantly. So running Varnish along with a full-stack Web server can negatively affect its performance (unpredictable load). Such configuration is counterproductive to the essence of caching. This is why we run Varnish and only Varnish on your Cachoid. Simple, efficient, and predictable.