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I am designing a simple fail over system with just a primary and standby server. The main one will be in our office, while the standby will be on the cloud. I was reading about virtual IPs and how they provide 'failover' typically for load balancers.

My question:

How are they able to switch so fast?

My limited understanding of DNS data is that they are cached on dns servers worldwide. Surely, it will take time to propagate any changes.

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Virtual IPs can typically only be used within a single network, e.g. in an Oracle RAC cluster. You can't really do that between the office and the cloud.

You may have also heard of Anycast IPs but that needs a much more advanced network infrastructure than you probably have.

It also depends on what kind of server you're building. Some services are designed to support multiple servers - e.g. DNS. Some support primary/secondary servers - e.g. SMTP. Some support master/slave setup - e.g. most databases. And some can be configured in a way that it doesn't matter which server you access - e.g. stateless web servers.

Forget Virtual IPs / Anycast IPs - that's an advanced level.

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  • Thank you. Since my on prem server and cloud server are on different networks, I cannot use virtual IPs then. I guess I have to setup dual load balancers and use virtual IPs. Sep 8, 2021 at 3:53
  • @user1034912 it very much depends on what you're trying to achieve. If I were you I would simply have your web server in AWS and be done with it. Cloud instances are typically more reliable than some office equipment that can suffer from HW issues, Aircon issues, uplink issues, etc. You may be needlessly overcomplicating a simple task of hosting a web server in the cloud.
    – MLu
    Sep 8, 2021 at 4:48
  • My Server currently has 7,000+ MAUs so it's pretty important to keep it up and running Sep 8, 2021 at 5:34
  • @user1034912 the more the reason to move it to the cloud ;)
    – MLu
    Sep 8, 2021 at 5:35
  • Only 10 of them are paying though :( Sep 8, 2021 at 5:37

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