Monday, August 17, 2015

domain name system - Multiple DNS servers for website failover



I know this is a bad "solution", if its even one, but due to the circumstances I think it fits.



If Server A runs ns1.example.com and Server 2 runs ns2.example.com and both are hosting an exact duplicate of a website but each have www.example.com DNS A records pointing to themselves. Will this work as a cheap/fast (to setup) failover solution in case server A suddenly fails?



The way I see it, a downtime of 30min-1hr is of no real concern so DNS TTL can be adjusted around that time.



Answer




Will this work as a cheap/fast (to setup) failover solution




Not really.



DNS Round Robin is not really a failover or HA solution. It's more of a load balancing solution. If one of the servers fail, about half the requests to your website may also fail until the record of the offline server is first removed from the DNS server and then you have to wait for the TTL value to expire after it is removed and wait for the end systems to clear it out of their cache.



edit: If you are looking to setup both NS servers to serve the same zone with different records, that is likely a non-starter.



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