We have had a Power DNS recursing cacher deployed at one of our busiest sites for a few months now and I thought others might benefit from some real world performance info. This is running on some older hardware.. dual Xenon 2.8Ghz system with 4G of ram and the only job it’s doing is running this recursor. These three graphs tell the tale. The first shows that the system is handling peaks of about 3800 queries per second and that about 99% of those are being answered in a fraction of a millisecond. The second shows that cache hits are averaging about 70-75% and the third shows that it’s doing this work while using at most one quarter of the CPU. Add to those impressive performance levels that I’ve had zero issues since putting it in production six months ago.
I thought some might find this interesting. Most who work outside of tech (and many inside tech) never see data centers like this. To get to our company servers in this hosting facility I have to pass through two man traps and a total of 5 doors with hand scanners. In addition, each rack of equipment is locked with a unique 6 digit code. There are hundreds of cameras inside the main datacenter and guards constantly watching from a secure room.
Here’s the scenario.. It’s 1 am and I have to shut down a critical linux server to relocate it in a rack to make room for new equipment. It should have been a 5 minute job.. but on powering up the server it refused to boot past printing the word ‘Grub‘ on the screen. This isn’t good.. this server is needed by a couple hundred thousand customers and rebuilding it wasn’t planned or scheduled.
If you have to do any sort of reporting using mysql or other databases you will probably need to use relative date ranges that don’t depend on what day the report is being run. That is if you need a report for ‘last month’ that runs from the first to last day of the previous month.. or previous 3 months etc but not include any days in the current month. Here is a small collection of queries…
