Re: HA Active/Active Cluster
Hi
On Wed, Nov 27, 2013 at 11:19:15AM +0100, basti wrote:
> Hello,
> I plan to setup an Active/Active HA Webserver with 2 VPS.
> I read something about Heartbeat/Pacemaker and HAProxy but what do I
> need? What is overkilled?
heartbeat/pacemaker are good for making an IP address "float" between
servers: if one server goes down, the IP address will migrate to
another server. This avoids a single point of failure here. [1].
HAProxy is good too, but solves the problem differently: Instead of
letting your servers accept connections directly, you force everything
to connect to haproxy, which will then proxy the connection to
whichever server is up. This gives you some simple load balancing
too. But it gives you a single point of failure on the proxy.
Either way, TCP connections will break if a back-end server fails - it
will be up to the clients to re-establish connections. For browsers,
this should not be a problem, but if you run a web application which
relies on long-lived connections, this may be a concern.
Which one is best for you? It depends... How much complexity are you
willing to suffer? Which failures are you trying to guard against?
Depends on your situation...
Whichever solution you choose, make sure you get well aquainted with
it and know the limitations of it; if the requirements change, this
may change the tradeoff between load balancing, high availability,
performance, recovery time, complexity etc.
> And is it possible to setup this with only 1 public IP per Server?
> Is there an Tutorial somewhere?
I'm sure there is - google searches for "haproxy debian tutorial" and
"pacemaker debian tutorial" both give sensible results :-)
[1] Well: it avoids *this* single point of failure. You may well have
single points of failures elsewhere, both in front of and behind
the web servers...
--
Karl E. Jorgensen
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