For the price, it’s hard to beat the EC2 Micro instance. But, if you have even a little bit of traffic, don’t expect to run a stock AMI without feeling some performance pain. After migrating this blog, we noticed that being logged in (meaning no wordpress cache hits) literally slowed the server down to a crawl. Just clicking around wp-admin a few times would drive load up to 12-13 and stuck the virtual server in 98%st. Apache connections were tweaked, mysql database settings optimized – traffic was really light (2-3 users) and the damn thing was unreachable! It was time for some PHP acceleration…

W3 Total Cache for WordPress

We switched to W3TC from WP Super Cache over a year ago. Besides offering more caching options (minify of static resources, embedded CDN setup), it’s also possible to use a combination of memcache and opcode caching. Back then, we didn’t have need of such heavy-duty, but it was nice knowing they were just a couple of clicks away.

Fast forward to 2011 – after our well-received devops series, we’ve seen some explosive growth. The continuing problems I described above had to be solved if we were to continue to grow our audience. As this system is a WordPress server, a PHP accelerator seemed the most logical solution.

APC Opcode Caching to the rescue

W3TC recommends APC Opcode caching and our Ubuntu based instance allowed us to easily install it:

apt-get install php-apc

W3TC offers a default configuration which you can append right to the php.ini:
sudo cat /opt/bitnami/apps/wordpress/htdocs/wp-content/plugins/w3-total-cache/ini/apc.ini >> /opt/bitnami/php/etc/php.ini
Restart Apache, to register the changes:
sudo /opt/bitnami/ctlscript.sh restart apache

Now, you should see the Opcode selectable in the W3TC options:

We use the “Opcode: APC for caching” setting for Page, Minify and Object caching and leave Database alone (as recommended in the fine print).

After restart, Matthias and I clicked around a bit. Wow, what a difference! Both in the front-end and wp-admin. Whether logged-in or not, the site was noticeably more performant and sluggish clicks in the backend were much snappier. It’s fun again to write posts, manage tags and scour comments for spam!

Professional Grade Virtual Computing for “Free”

In case you missed my other posts on acquiring, maintaining, backing-up and monitoring your virtual server, here’s the complete list:
• EC2 setup : Migrate Your WordPress Blog to a Bitnami EC2 Instance
• Backups : Poor Man’s Automated Snapshots for EC2
• Monitoring : Cloudkick Monitoring for EC2