On the MySQL Performance Blog there's a recent post looking at the impact of SSL in regards to the overall performance of your application. This is part one of a two part series and focuses largely on the results of two tests - one with connection pooling and the other to evaluate connection time.
Some of you may recall my security webinar from back in mid-August; one of the follow-up questions that I was asked was about the performance impact of enabling SSL connections. My answer was 25%, based on some 2011 data that I had seen over on yaSSL's website, but I included the caveat that it is workload-dependent, because the most expensive part of using SSL is establishing the connection. Not long thereafter, I received a request to conduct some more specific benchmarks surrounding SSL usage in MySQL, and today I'm going to show the results.
He details the environments used for testing including the hardware specs and the version of the software installed. The scripts (really just bash scripts that call sysbench) are included in the post and the results of the tests are both graphed out and dumped in tabular form. The results are pretty surprising, mostly having to do with just how much of an impact the SSL has on the the requests. He makes a few recommendations at the end of the post on how you can mitigate these problems though (hint: it's not about MySQL per se).