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Heart beat servers or a simple failover server
Posted: Fri Sep 25, 2009 7:45 am
by jaoudestudios
If 1 server goes down, is it possible to have another fill the void (at a different location)?
I am aware of heart beat. Is this the only way? Is it easy to setup?
Thanks
Re: Heart beat servers or a simple failover server
Posted: Fri Sep 25, 2009 8:33 am
by VladSun
What do you mean by "server"?
What do you mean by "at a different location"?
Re: Heart beat servers or a simple failover server
Posted: Fri Sep 25, 2009 8:38 am
by jaoudestudios
Basically, I have a webserver with rapidswitch in london. If this goes down can it failover to my spare box at home?
Re: Heart beat servers or a simple failover server
Posted: Fri Sep 25, 2009 3:06 pm
by VladSun
The simplest fail over requires that the slave (your machine at home) is able to acquire the same IP address as the master one. This in turn, usually requires that the two machines are in the same physical network, so IP routing can be done. In your case I really can't see how you can accomplish this.
Because your machines have different IP-s, you should also modify your DNS zone file when fail over occurs. This means that you have to use very short TTL for your domain zone (e.g. one minute). This also means that in the worst case you'll have DNS-TTL-time of down time (because some users may already cached your DNS answers). A short TTL will increase the number of DNS requests your DNS server have to answer.
Finally, you have to take care of user sessions related issues - you need to replicate these sessions on the slave machine. Maybe a DB session storage would solve this issue.