[CentOS] Load balancing...

[Jay Leafey]

I've used round-robin DNS with good success, but I added some additional 
tweaks using Heartbeat to manage the actual addresses.  A typical case 
is where you have two systems that will be used to offer a service.

Each machine has it's own IP address, but in addition there are a pair 
of IPs for the SERVICE that are managed by Heartbeat.  The round-robin 
DNS entry points to the service addresses, not the "primary" addresses 
of each node.

When one node goes down, Heartbeat on the other node causes it to take 
over the failed node's service address.  This minimizes the time where 
the resolved address points to a dead node. so the window for failure is 
narrowed significantly.  We've used this for DNS server, LDAP servers, 
and simple web servers with good results.

This is NOT an absolute fail-proof way of doing it, but it's easy to 
implement and is "good enough" in many cases.  We've had some situations 
where Heartbeat didn't detect node failure quickly, but overall we've 
gotten acceptable results.

Your mileage may vary!
-- 
Jay Leafey - jay.leafey at mindless.com
Memphis, TN
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