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.
Time Warner has been offering faster cable modem speeds lately for much the same price as slower speeds a couple years ago. When I got the new modem I noticed there didn’t seem to be a way to put it in bridge mode to work with the linux router I already had. After a little digging I found that the management page for doing this was ‘branded out’ and the link to it was removed from the interface.
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.
I’ve heard some… odd comments on the new Chevy Volt and just wanted to point something out. The above line ’40 miles to the charge’ is being said with a negative connotation… even suggesting that the battery should be the backup to the gas engine. The average commute is 20 miles.. and this was the target for the battery capacity… so lets do a little back of the envelope math.
Since this is the season around here for frequent thunderstorms.. I thought it might be interesting to look at what a typical storm cloud might ‘weigh’. These things are floating above our heads.. and it’s just not something most people ever think about. They are all unique of course.. so here are some baselines.
A storm cloud that is 1 sq/mi and 33k feet tall (medium height for what we get this time of year) with an average density would hold about 563 million pounds of water.
Continuing on yesterdays posting about RFID recycling bins. It seems our own city council wasn’t aware of the tags either until after the Tara Servatius show where she covered the story (after I scooped her army of research interns). Reading a little more about these.. it seems to be a world wide phenomenon as these chipped cans are showing up in cities and many countries around the world.. with much the same negative reception.
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..
