There are many opinions in the air about the impact that virtualization has on performance, so I thought a short blog would be good to explain (as best I can) virtual machine performance characteristics with pointers to relevant benchmarks and technical papers.

My background is that I was an early Product Manager working on VMware ESX Server (from version 1.5) and among other things ran product management for VMware for a few years. As a product management guy, I kept track of the output of the engineering performance group, and as a result had a reasonable high level (although never code level) understanding of the whys and wherefores of virtualization performance. Although I’m not as fresh on virtualization as I once was, I’ll try to do my best here. I also want to thank Steve Herrod at VMware, and Simon Crosby at Citrix for providing a technical sanity check on the blog contents, although I retain responsibility for any mistakes and oversights.

Memcached will dramatically speed up MediaWiki. Some pages on my site, like the Main Page took 40 seconds to load before Memcached, but only 7 after installing Memcached. "Memcached is a high-performance, distributed memory object caching system". Memcached is essentially a database caching system which is object orientated, and works even if the database is updated. (MySQL caching discards the entire cache when a table is changed)