Interesting stats

As a follow up to Matt’s September wrap up post, I thought it would be fun to post some more technical stats about the current WordPress.com infrastructure:

• 80 physical processors
• 139GB of RAM
• 91 hard drives with a combined total of over 15 terabytes of storage space
• 2000 database queries per second spread over 40 MySQL instances
• Over 8 million objects stored in memcached serving over 8000 requests per second

The best part is that this is just the beginning! There are many more exciting things to come. Next up — expansion to 2 additional datacenters in the US.

Load balancer testing

Over the past week here at wordpress.com, we have been doing some experimentation with various software load balancers. In the latest test, we are using Pound with a weighted round-robin algorithm between all of the web servers in a given datacenter. The individual weight takes into account hardware differences and any other tasks that server may be doing. So, a dual processor server would receive more traffic than a single processor machine. The tests have been going really well so far.  Once the testing is complete and we have decided on a solution, I will post about the various things we tried, pros and cons of each, etc.  The graph below shows the load averages of the various web servers over a one week period. I’ll let you guess when the test began Pretty dramatic difference, eh?