Active/backup configurations and load balancing with Keepalived
A Linux server that is set up as a load balancer for multiple worker servers and keeps the service available, even if any of those workers fail. However, the load balancer itself becomes a single point of failure in that scheme, unless the administrator also takes care to provide a failover mechanism for multiple balancers.
The usual way to achieve failover is by using a floating virtual IP address. Suppose www.example.com is configured to point at 192.0.2.100. If you assign that address directly to a load-balancing server in a 192.0.2.0/24 network, it becomes a single point of failure. However, if you set up two servers with primary addresses from that network (say, 192.0.2.10 and 192.0.2.20), you can use a special failover protocol to allow two or more servers to decide which one will hold the virtual 192.0.2.100 address and automatically transfer it to a different server if the primary server fails.
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