Re: PostgreSQL and 2-node failover cluster solutions

On Sun, Oct 06, 2002 at 03:21:14PM +0200, Ragnar Kjørstad wrote:
> Well; if you have a single NetApp then you still have a single point of
> failure (avoiding that is the whole purpose of failover, right?), and if
> you have two of them then it's one pretty damn expensive
> postgresql-server :)

Indeed we run our Netapps as a clustered pair. If you already have the
facilities available or can get them for a good price second hand, then
I am happy to let the group know that running PostgreSQL servers on Linux
and Netapps is not only possible, it is a fast, reliable and stable
platform.

> Anyway.....

> > I presume you are using it to failover PostgreSQL servers?
>
> No, currently we're only using it for failover lvs- and file-servers.
> The principle is the same though: Heartbeat runs on two servers
> connected with multiple "heartbeat-channels" (ethernet, serial....).
> They constantly monitor each other, and if the secondary server looses
> contact with the primary it will start the "services" locally. In your
> case the services would be an IP-address and the postgresql-server.
>
> You also need some "fencing" to make sure that the two servers don't
> both start postgresql by accident. This is done with "stonith" (Shoot
> the other node in the head) - before the secondary server starts
> postgresql it will cut the power to the primary server to make sure it's
> not up.
>
> That's pretty much it.

Great, sounds very similar to Kimberlite, and also to our requirements.
I will give it a test.

> Be awere that failover doesn't solve any problem in the world though: If
> postgresql corrupts it's files, both servers are screwed. Also, failover
> will complicate the setup, and in general a more complicated setup means
> more downtime (operator-error) - so, make sure you read the
> documentation and understand how it works (or pay someone to do it for
> you).

Naturally, that's why we are after as simple a solution as possible.
That is also why we went for a simple, free and open database like
PostgreSQL rather than a more complex system like Oracle (of course,
cost was a factor also :).

Thanks for the cluster info. If anyone wants to discuss HA PostgreSQL
setups more, drop me a line.

Cheers,
Chris.