Combat server downtime by duplicating server and re-routing when main server is down

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http://serverfault.com – I have a CentOS server which at times either crashes or gets attacked with DDOS. At the moment I have an off site backup which is filled up with 1.7TB of data. I'm currently paying as much for the backup as I am for the server and I was looking for advice from experienced people as to what option is best to proceed from here. Would it be a viable solution to ditch the offsite backup, and instead purchase an additional server which is an exact duplication of the first server. So if the first server is down, users are re-routed to the second server without noticing the first server is even down (HowTos)