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.
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…
For those who don’t know.. As a nation we have essentially decided to give up our manned space program. While NASA has done amazing things with robots and satellites in space the one aspect that really captivates is manned exploration. As with most huge projects, things haven’t exactly gone as planned with the shuttle or space station over the last 30 years. But now as reality sets in and we see the ending of the shuttle program it strikes me as a milestone that the United States will not have a way to get people into space forcing us to rely on the cooperation of others (who are not our friends) to do so. I wanted to share a few things for those who are interested. From Penn Jillette in How to Play In Traffic
This is an update to my initial posting last July. It didn’t take long to figure out the lead batteries were not going to cut it for the sort of high performance bike I had in mind. So shortly after I moved I replaced them with a LiFePO4 pack from Yesa. I got this straight from the manufacturer in China at a considerable savings over other similar quality packs from retailers here. I can only speak for my experience.. but the guys at Yesa were top notch to deal with and after more than 6 months putting their batteries to work I’ve had no problems. The Li pack is lighter and I relocated it for better balance on the bike. With a fresh charge on level ground it can sustain 40… but 35 is a normal top speed once you get past the first few miles.If I had it to do over.. I might go with a 72v setup and a motor with more windings. That would allow for lower power draw but still ample speed when you need it. Continue Reading for more technical details..