[CentOS] Linux HA or Heartbeat IP address question

[Ian Forde]

On Tue, 2009-02-03 at 13:58 +1100, Devraj Mukherjee wrote:
> Hi all,
> 
> I am following the guide on HowToForge to get Heartbeat going for two
> Apache web servers
> (http://www.howtoforge.com/high_availability_heartbeat_centos), a
> quick question for anyone who might have a similar setup.
> 
> Do I have to assign the service IP to either of the NICs or does
> Heartbeat do that automagically?

Heartbeat does it for you - basically, Heartbeat for apache can be setup
in less than 5 minutes. It's no more complicated than the link you
posted.  Each box has its own address, then there's the VIP.  To get a
little more advanced, you could configure a private link between them
with a crossover cable and monitor that in heartbeat if you wanted to,
but it's not required.  Also, I'd turn off auto_failback... but that's
just me.

Some notes:

1. Disable apache from automatic startup via:
	chkconfig httpd off
2. Enable heartbeat to startup automatically via:
	chkconfig heartbeat on
3. Consider using the aforementioned private link, as the broadcast
traffic can be maddening on a busy segment.
4. Consider using a private vlan rather than a crossover cable.  If a
crossover cable, or either side of a private link dies, and you've got
STONITH enabled, both nodes can, under certain circumstances, kill each
other.
5. Consider installing mon as well to monitor the cluster.
6. auto_failback means that that if you default to node01, then node01
fails, as soon as its back up, it'll fail back to node01.  That can be
good, but it can also be very bad... think of the case of using
Heartbeat with mysql, and ask yourself how often you want to fail over a
live database cluster. ;)

Have fun!

	-I