[geeks] Remote Failover

[James Fogg]

> >> Because the machines are a thousand miles apart.  I'm not
particularly
> >> concerned with balancing, really.  And I can always set the TTL
really
> >> low for that one record, no?
> >
> > F5 load balancers and F5 3DNS.
> >
> > BTDT, worked like it's supposed to.
>
> What if I lose network connection to the load balancer?  Do I need
> multiple balancers for redundancy?  Does that work exactly how it's
> expected to?
>
> Forgive me, this is the first time I'm using any technology like it.
> Also, I don't suppose there is open software for doing this stuff...


You would use a load balancer in each datacenter. The load balancers
report to the 3DNS(s) server about the health of the web servers behind
the balancers. If servers begin to become unresponsive, 3DNS makes
decisions about how much (if any) traffic to send to each DC. You can
have the 3DNS server in an unrelated DC for additional redundancy, and
you can have multiple 3DNS servers. The 3DNS server(s) also make queries
to the balancers to check network performance, and may cut off an entire
DC if need be based on network performance.

For this to work, you have to have 3DNS be authoritative DNS for your
domain, or at least for the machines in the DC's.

I used this architecture with web servers located in DC's on each US
coast for a service that took 800 million hits/day. It was an absolute
charm.

Think if the architecture this way: The load balancers manage server
performance and availability within a DC, and 3DNS manages performance
and availability of DC's.

I have extensive experience with F5 solutions if you need help.