Drupal 7 supports Memcached, Redis, Varnish, MongoDB, APC, Filecache, and Boost as cache backends - not to mention good old fashioned databases! It even supports putting individual cache tables into different cache backends. With so many options, choosing the right configuration can be paralyzing. We've built out a multi-server testing platform using representative Drupal 7 install profiles, makefiles, and workloads to answer questions like:

• Which tables should be offloaded to which cache backends?
• How do different cache backends cope with cache clears?
• What is the impact of common performance tunables (like Memcached compression or APC shm_size)?
• Do different cache backends scale differently with load?
• What happens to scaling when multiple web nodes use the same cache?

Tools used for our analysis will include statsd, R, graphviz, D3.js, and Tracelytics.