Cross-colo fail-over design, DNS level fail-over?

Question

I\'m interested in cross-colo fail-over strategies for web applications, such that if the main site fails users seamlessly land at the fail-over site in another colo.

Th

Answer 1

As for DNS, I like to reference, "Why DNS Based Global Server Load Balancing Doesn't Work". For everything else -- use BGP.

Designing networks in order to load balance using BGP is still not an easy task and I myself certainly am not an expert on this. It's also more complex than Wikipedia can tell you but there are a couple interesting articles on the web that detail how it can be done:

• Load Balancing In BGP Networks
• Load Sharing in Single and Multi homed environments

There is always more if you search for BGP and load balancing. There are also a couple whitepapers on the net which describe how Akamai does their global loadbalancing (I believe it's BGP too.), which is always interesting to read and learn about.

Beyond the obvious concepts you can use software and hardware to achieve, you might also want to check with your ISP/provider/colo if they can set you up.

Also, no offense in regard to your choice of colo (Who's the provider?), but most places should be setup to deal with downtimes and so on, they should not require you to take actions. Of course floods or aliens can always strike, but in that case I guess there are more important issues. :-)