Soft Layer actually has a good solution for this with their global load balance and private ethernet solution if your looking for a geographical setup. There are many other providers who could provide affordable high availability solutions too. Make sure you do your research on a provider carefully. High availability is sometimes promised but unable to be delivered on.
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i need help in High Availability and Disaster Recovery,
what is the best approach for HA and DR for 2 web server and 1 database server ?
rapid growth is also a major concern.
Are you looking to implement this using shared accounts, VPS nodes, or actual physical nodes? The shared account approach is cheaper but performance-averse. Anyway, high availability AND failover effectively doubles the number of servers that you need. Depending on your current capacity needs, You might be able to collapse the 3 servers that you have into two servers (over time becoming N+1) and one DR (N+1 as well) server. Three-way database replication is the best approach in this case.
It's difficult to recommend a solution with so many unknowns. What is your current resource usage? What do you project in terms of growth? And, last but not least, what is your starting budget for this task?
Here's what I'd recommend: 1 web and 1 db server in each location, with the main location having the master MySQL server and the second one a slave MySQL server which turns to master in the event one of your locations goes down. There is a bit of configuration to be done here and there but it's possible without extra hardware for load balancing. For failover on the cheap you can go with DNS failover.
This sort of setup will depend on how your application is built, assuming it is for Linux/Apache Mysql and PHP. You need to talk to some hosts and get a quote, though any serious datacenter will rarely have any trouble.
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