Do you mirror? (If so, how?)

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Posted by boomtown, 05-03-2007, 06:37 PM
Ok here's a potentially dumb newbie question, but I have to know. How many of you mirror your sites, and how do you set it up? Is it as simple as getting 2 different webhosts, and setting your DNS settings to primary: DNS.HOST1.COM secondary: DNS.HOST2.COM And, in the event of HOST1 going down, will the magical internet genie know to direct all your traffic to HOST2? Also, what's this I've heard something about a "round-robin DNS" setup? I read it in a thread in response to someone who was trying to manage bandwidth. The suggestion was to set up a bunch of mirrors with a round-robin DNS so that traffic gets split equally. This is all very interesting & new to me. How do I do it?
Posted by d33pa, 05-03-2007, 07:55 PM
if you setup your dns records for different servers, then if the 1st server cannot be reached, the 2 nd server will pick up the slack, and so on. this is a pretty easy setup if your sites are static and no databases, etc are involved. It gets more involved once you are hosting dynamic sites because you have to make sure that the data is replicated live on both servers. you can also look into clustered servers. i think that is the best way to go to prevent any hardware failures and to provide redundancy for loads.
Posted by David, 05-03-2007, 08:01 PM
boomtown, As noted by d33pa it's really only feasible in the event that your site isn't database driven. If it is then you still have a single point of failure (potentially). One option would be to segment your database driven content and 'cache' as much as possible. It's definitely one of the ways to go if you want to increase your reliability / spread your bandwidth usage.
Posted by ldcdc, 05-03-2007, 08:08 PM
As far as I understand it, part of your traffic will always go to server1, and the other part to server2. I think that what you're after is a DNS Failover service, where the servers are monitored, and as soon as server1 is down, the DNS records are modified and the traffic sent to server2. I'm not an expert in these matters though, so do take my advice with a pinch of salt.
Posted by layer0, 05-03-2007, 08:10 PM
That is 100% correct. www.dnsmadeeasy.com offers failover DNS.
Posted by bear, 05-03-2007, 08:54 PM
Since it's more a technical question than a webhosting one, moved to technical and security.
Posted by wKkaY, 05-03-2007, 10:26 PM
Web browsers (at least with IE6++ and Firefox 1.5++) can failover when there are multiple A records for a domain. If the host doesn't accept the TCP connection (i.e. if it's unreachable or the connection is refused), the browser tries the other IPs. This helps improve availability in the lower layers, but it cannot overcome application-layer problems such as webserver misconfiguration, scripting errors, etc.