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DNS based Website Failover Solutions?
Chase asks: "I run a couple of websites(including for my work). I'd like to have a backup web server that people would hit when my server goes down. My primary host is on my companies T1 line and even though I've had my server die once the most common reason for my sites to be offline is that our T1 goes down. I've looked at the High-Availability Linux Project but it seems that almost everything there is for failover using ip takeover which isn't an option if my network link dies and my backup server is on a different network. ZoneEdit seems to offer what I'm looking for but I'm wanting a do it myself solution. The only software I've found is Eddie and it seems to have stopped development around 2000. I know DNS based failover doesn't give 100% uptime but with a low cache time and decent monitoring it seems like it's the best solution for having my backup server at a differnt location and on a differnt network. Anyone know of a good solution? (Using Linux and/or Solaris hosts)"
If I understand you correctly you you are looking for a F/OSS project to do what you are after.
However if you do actaully have a budget to spend have a look at the 3DNS product from F5 Networks. it does the failover you describe and although it works better if it is intereacting with F5's server load balancing product, it can still monitor and react to standard web servers becoming unavailable.
The Romans didn't find algebra very challenging, because X was always 10
1. Use colocation/Web hosting as the primary site. Their uptimes are usually very strong.
2. You will need a second line. Mandatory. If you really want insane uptime, you'll need dynamic routes ala BGP from both ISP's. If you don't need that much, you could maybe work with an automated probe-and-dnsupdate script which can run outside the network. It would switch the primary DNS to and from the backup IP address which is on the isolated network.
3. Have an equalized DNS entry for both IP addresses. It gives the client a 50% chance of connecting once its dead, but its better than nothing.
4. Tell the site visitors to connect to www1.mysite.com if they're having troubles reaching your site and have www1 pointing to your backup IP. Make sure your DNS servers are network redudant as well, or the whole excersize is pretty pointless.
Bye!