Physics, PowerDNS, life

Posted by bert hubert Tue, 28 Mar 2006 20:48:00 GMT

Ok, this blog is not all about PowerDNS. Seriously. So, first some Physics. I used to be a physics student at Delft University of Technology, but I dropped out halfway through. That doesn’t mean I lost interest in hard science though.

I have a strong interest in ‘fringe science’. In my not so humble opinion, quietly shared by scientists I know, physics is focussed too much on confirming current ideas, whereas doing research into ‘interesting’ results is frowned upon.

I previously wrote a bit about this here.

Some of the things I keep an eye on are

  • “Cold fusion”
  • The gravity anomaly described in the link above
  • Gravity shielding

Cold fusion

The cold fusion bit is interesting enough. There are literally thousands of results but none of them has proven able to convince mainstream physics. Partially this has been due to the experimenters, which have sometimes made huge fools out of themselves, or have even committed fraud.

However, even when people do come along with solid results, they are faced with incredible amounts of criticism. You might as well try to convince people child pornography is art. The results on your career in physics are highly similar.

I’m currently of the opinion that there is so much smoke surrounding cold fusion that there is bound to be some fire.

Gravity shielding

Has been interesting too. Realise that nothing, and I mean nothing affects gravity. It goes through everything. We can’t create it, we can’t stop it. The saga started out with measurements by the secretive Evgeny Podkletnov, who claimed to have observed a slight decrease in the force of gravity above a rapidly spinning superconducting disk. High temperature superconductors are excellent at conducting electricity but their mechanical properties are somewhat lacking, and people have had a hell of a time getting such a disk to rotate at speed without disintegrating.

NASA sunk a lot of effort in trying to reproduce his results, but sort of failed. The guy in charge, David Noever is currently nowhere to be found, after he also researched gravity anomalies during solar eclipses.

Then another scientist, Ning Li studied the effect and vanished, as far as I understand it. Popular Mechanics ran an article on her. In the mean time, Podkletnov is now supposed to be part of secret military research in Russia. The stuff of conspiracies!

This strand of interest appeared to be slowly dying off though when suddenly ESA and US Air Force sponsored scientists presented this paper, on the ESA website no less.

In this paper, they report finding a 1-in-10000 change in gravity above a ring of niobium or lead when, cooled to liquid helium temperatures, it is rapidly spun up or down.

They mention that they’ve spent three years trying to spot errors in their experiment, which has been run 250 times.

Well, why is this important? As I described in my own page linked above, quantum mechanics and (general) relativity collide. Gravity is firmly in the relativity domain, superconductivity is as quantum mechanic as it gets. Also, nothing else has ever changed gravity.

This discovery could quite literally put physics on its head - which is high time, things were getting decidedly boring.

PowerDNS

Ah, that thing. Well, not a lot to report. Everything ticking over just fine. Did discover that an important part of DNS, the ‘any query’ is completely unspecified by the RFCs. You can try to read what you have to do into the ancient writings of Mockapetris & friends, but I’m not to sure. Decided to emulate BIND instead, which is also the easiest thing to do.

I’m trying to double the recursor performance (again), but this appears to be hard work. Perhaps DTrace on the Niagara can be of some help.

Life

Trying to relax a bit, worked too hard on PowerDNS and other projects. Working too hard makes me unfriendly and irritable, which is not a pleasant thing.

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Heading up to big PowerDNS recursor deployment

Posted by bert hubert Sat, 25 Mar 2006 15:02:00 GMT

For far too long now we’ve been working on implementing custom features for a big internet service provider here in The Netherlands and it appears we are almost there.

But then again, I’ve thought so a number of times already. The recursor (or resolver) of a network is one of the most crucial components of providing good service.

Put simply, a broken nameserver is perceived as a broken network. A slow nameserver means a slow network. So providers are understandably nervous about migrating to PowerDNS!

Some events may be forcing their hands however. To help ease migration fears, I’ve written dnsreplay_mindex, a tool that replays recorded DNS traffic (which you should anonymise using dnswasher if you plan on shipping it to me!) against PowerDNS, and shows statistics relative to your original nameserver.

I’m now confident that the PowerDNS recursor performs, in many cases, thousands of times better than the competition. Ok, that sentence has a touch of marketing to it. Just a touch. But I’m currently benchmarking at three times the original speed and dropping 30000 times less packets than BIND 8.latest.

That does not mean to say the PowerDNS recursor is perfect. It isn’t, not by a long shot. Even yesterday it turned out one of the more unique features of PowerDNS, the ability to forego hammering broken nameservers with queries that time out, had a cache that was cleaned in reverse: all NEW entries were being removed each minute.

The stunning thing is that it worked fine anyhow, just ate heaps of memory and performed some needless queries - which other nameservers perform all the time in any case.

Furthermore, the recursor carries IP addresses around as full blown strings, for which there is no excuse.

Update: I fixed this here

So there is still work to do, but I’m confident we can migrate at least one of the target servers to PowerDNS on Monday.

In other news, it is a bit quiet on the Niagara (Sun T2000) front, I’m mostly reading up on the unique features of its CPU before delving in with code.

My current aims are to make PowerDNS really fast on T2000 and write a HOWTO about the process, allowing you to benefit from this architecture as well.

On the human interest front, it turns out that leaving the dough to rise in the fridge does indeed produce something that is more like the kind of dough I want, but I’m still not there! I think I’ll aproach my favorite pizza restaurant soon and hope they are willing to share. I already have a proper pizza oven.

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