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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: 1.2.3.4 at datacenter A is not reachable from the outside world, how does my second server at IP: 4.3.2.1 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

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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  • Are you saying he needs a third server?
    – johnny
    Aug 25, 2016 at 17:56
  • Well, at least two load balancer units in some form of cluster configuration (operating as one unit) for redundant load distribution/failover. Or a resilient cloud service.
    – ErikE
    Aug 25, 2016 at 18:09
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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? Nov 22, 2013 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, 2013 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. Nov 22, 2013 at 11:35
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    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, 2013 at 12:32

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