On Wed, 2011-01-12 at 13:22 -0500, Tom Allen wrote: > Here's one reason you have your DNS redundant: Say you work for > foo.com, and I ask you to send me product details, because you make a > great product. You email me, and the email makes it off your server, > and your server crashes, taking your DNS with it. Spam filter on my > side looks up your domain, it doesn't resolve, and I send your email > to /dev/null. Not hearing from you, I buy Baz.com's version of your > product.
Great example, but short of that scenario, not really sure how many others would benefit you like that. With DNS still being up with everything else down. > DNS is light and easy to configure, and trivial to get spread across > multiple networks. Names that don't resolve suck -- it slows things > down while resolution attempts to happen. You can experience the same thing as it goes to hit the various DNS servers in order, if the initial ones are unavailable. Even though you end up resolving, you still get slowness. > Additionally, many servers will cache your non-resolution for an > hour or more, and so if your server is "down" for 5 minutes, your > outage becomes much longer with a cached no-resolve result. Now that I could see having a greater impact. I haven't really experimented with what a DNS server does if it does not get a result. But caching nothing seems kinda like a bad idea. One would think the software would know it did not get a result and maybe try again. I would think that to be different than getting a result and retaining that as part of cache. I might see about playing around with that at some point. If DNS servers do cache no result just the same as having a result. Then it makes much more sense as to why having two or more. Thanks for the info, two good scenarios I really had not considered. I have always run at least 2 DNS servers. Just have kinda always asked why, and seems like it would be a good rule of thumb across the board :) -- William L. Thomson Jr. Obsidian-Studios, Inc. http://www.obsidian-studios.com --------------------------------------------------------------------- Archive http://marc.info/?l=jaxlug-list&r=1&w=2 RSS Feed http://www.mail-archive.com/[email protected]/maillist.xml Unsubscribe [email protected]
