On Sun, May 20, 2012 at 8:43 PM, Nilesh Govindrajan <[email protected]> wrote: > On Mon, May 21, 2012 at 1:17 AM, Alan McKinnon <[email protected]> > wrote: >>> Slow connection. See my previous reply to the list. I'm using pdnsd, >>> which can persist records and has every damn feature I wanted. >>> >> >> Fair enough, but consider this: >> >> If your connection is slow, the only thing you speeded up is the DNS >> lookups. Thereafter, everything else is still as slow as it ever was. >> And if you feel the need to speed up DNS lookups then the odds are very >> good that "everything else" is too slow i.e. not exactly usable. >> >> We get this a lot from our customers too, and the advise we give them >> is to look closely at their traffic throttling. In almost every case >> all UDP traffic has had the living crap throttled out of it somewhere >> by folk that don't really think things through, severely affecting >> dns and ntp as well as AV streaming. >> >> Throttled DNS rapidly gets out of hand, IIRC the last time we did some >> measurements it only takes around 5% of dns lookups to go wonky for the >> situation to rapidly spiral out of control - when dns fails the cache >> will try a TCP lookup and that's like wading through molasses. >> >> Our advice to customers is to first unthrottle dns and ntp completely, >> give it the highest possible priority (these are extremely light >> protocols and seldom show up on the radar when you do this), and see >> how that goes. >> >> It just seems to me that you *might* be trying a very unusual solution >> for a problem that is better handled one layer lower down. >> > > Strictly speaking, my connection isn't too slow. I have a transfer > rate of 64 K/s (might sound ridiculous to you, but this costs 18$/mo > here). > OpenDNS lookups from my connection take something like 300 msec+ and > Google DNS lookups around 50 msec. > > I can obviously use Google DNS, but as I said earlier, OpenDNS gives > me phishing protection and other that sort of stuff. > > And hence I must use a local cache.
Side note: Honestly, you should be using a local cache, regardless. It'll improve performance for you, *especially* when there's any risk of packet drops between you and the your ISP's core equipment. When I was on a 6Mb/s-down ADSL connection, the improvement I experienced simply from running bind9 as a recursive resolver was *massive*. I still do so, even though I'm now on a pretty reliable cable connection. -- :wq
