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Geo-DNS can be used to balance traffic across data-centers. I found this (old) article where it is described why Geo-DNS implies availability issues if one of the IPs (data centers) goes down.

Could someone confirm or deny such issues? Alternatives? Is a plain DNS with multiple A records better?

Thanks, Valentino

Valentino Miazzo
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1 Answers1

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Multiple A records is definitely not the answer. If one of your hosts dies, the DNS will still happily dish out the dead IP address.

GSLB (Global Server Load Balancing) or equivalent, will do health checks on all your servers, and will dish out a single IP for the server that is "closest" to the client, or multiple addresses but always excluding dead hosts, and will provide the preferred order based on "closeness". Fundamentally, you need something that performs a health check of all your hosts, and stops DNS from giving out the IP address of any dead hosts.

Anything that relies on the individual client's interpretation of what to do with multiple A records is going to cause issues, as each client (Operating System, browser, ISP DNS caching, etc.) is different.

John Röthlisberger
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