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I have a (web) server at a datacenter, which at times (as all datacenters do) has network failures (for like 10-30 minutes).

I have a second server at a different company (datacenter) which I could use as a failover solution.

Now, I was wondering how I could do that? Of course I can mirror the site. The problem is, how do I achieve this: When the main server let's say IP: at datacenter A is not reachable from the outside world, how does my second server at IP: automatically resume its work as main server ?

I don't think that round robin dns would be a solution, because half the requests will be directed to the server which is not reachable.

my servers are windows, IIs

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2 Answers 2

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You need to place the load balancer off site. Colocate a redundant hardware loadbalancer in a high-uptime third datacenter(costly but v.nice) or use a cloud service to deploy a redundant software load balancer(way cheaper). If you really can't get the budget, go dns.

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You are right - round robin DNS would not be a solution in this case. What you need is a DNS service that monitors the availability of your servers and switches over the DNS record for the web site to a failover IP once a problem occurs.

An example of such a service is DNS Made Easy's DNS failover service.

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thanks for the reply, is there any FASTER solution? the delay with this seems to be 2-4 min ping time + TTL of dns record which means on average 5-8 minutes. Isn't there any way for "instant" switch over? –  MIrrorMirror Nov 22 '13 at 9:05
If you plan to use only the two servers, then no. There are services like CloudFlare (cloudflare.com/overview) that provide cached content when your site goes down. You could also use a proxy server or a load balancer in front of your servers, but that's not very optimal when the servers are in different datacenters, and it adds just one more point of failure. –  Ketola Nov 22 '13 at 9:40
yeah that's my point, a proxy or a load balancer would still be in one of the datacenters that can fail, so if the datacenter network goes down, so does the loadbalancer/proxy. I will check out this dns mady easy's solution. thank you. –  MIrrorMirror Nov 22 '13 at 11:35
Also, as a side note, if your hosting provider experiences frequent downtime of 10-30 minutes, I would consider looking for another provider, or even AWS or some other cloud provider. –  Ketola Nov 22 '13 at 12:32

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