[GLLUG] Ubuntu Server Failover

[Andy Smith]

Hello Jean,

On Fri, Aug 02, 2013 at 10:54:38AM +0100, Jean van Wyngaardt wrote:
> Anyone have a good experience setting up a failover server, that also replicates the data from a master server?

Can you elaborate as to what services exactly you are trying to
increase the resilience of?

> I would assume rsync would do nicely for the data side, but I haven't really messed around too much with any failover apps before. Anyone have any favourites?

You will probably need to consider both the underlying storage (how
the data is made available to each node) and the failover (how the
outside world reaches the correct "live" node or nodes).

As far as the failover goes:

Pacemaker (what used to be heartbeat) has already been mentioned. It
is feature-packed but very complex.

Keepalived, like ucarp, is a simpler piece of software intended to
move an IP address or addresses around based on various
circumstances. So the idea being you have one live node and upon
failure keepalived will shift the IP address to one of the other
nodes.

If that would be suitable then I would go with it every time as the
simplicity helps with reliability (a certain percentage of outages
will be down to not understanding how pacemaker and its underlying
stack of software does things).

haproxy is a very nice open source load balancer with health checks
that can load balance HTTP, HTTPS or any other TCP-based protocol,
presenting a live IP on the front end and using a pool of nodes on the
back end.

A very common configuration would be two haproxy nodes with
keepalived flipping the IP address between them based on whether
they ping or not, then a pool of app servers behind haproxy.

Which of these solutions is best will depend on exactly what you're
trying to do, and I don't thin it's worth speculating on the storage
aspect until we know that.

Cheers,
Andy

-- 
http://bitfolk.com/ -- No-nonsense VPS hosting
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