Re: Adivice on master - master replication.

On 10/28/10 3:42 PM, Gregory Machin wrote:
> Hi
> I'm new to Posgresql.
> I have been requested to setup application level HA. The picture is, I
> will have 2 web servers behind 2 new work load balancers, so should
> one fail the NLB's will redirect traffic to the remaining server. I
> need a similar scenario for the Pgsql servers.
>
> > From my reading I need a synchronise master - master. so both servers
> need to be hot. Such that the web servers are unaware of which server
> the are communicating with, so should one  pgsql server go down there
> would be no interruption to the web servers.
>
> The processes need to be handled automagicly , well at least the fail
> over where the one server takes over the failed servers work load.
>
> Everything I have looked at has a single point of failure, generally
> the management application that looks after the replication.
>
> How do I achieve this .. I'm looking for a comprehensive howto .

the traditional method is a HA cluster with master/standy, sharing
storage via a fully redundant and dual pathed SAN.  all ethernet
connections are dual pathed, too, with redundant network switches.   the
master and slave run a cluster management package, such as linux
heartbeat, or veritas cluster service, which has distributed management
capability.   for robustness, you use a fencing systemm on the shared
storage so only one server is physically capable of accessing the shared
storage (this prevents a class off failures where the other server also
thinks its active and tries to mount and access the database storage).
The cluster manager also shares a single IP such that it reaches the
current master server, and your webfarm uses that IP for all database
operations.