Re: PG server clustering

On 10/17/2013 12:32 PM, Joseph Mays wrote:
> We are assisting in the system administration of a partner that uses
> PostGres in a mission critical position in their system. They have mail
> servers and other things that rely on 24/7 availability for the postgres
> server. They are running postgres 9.04 on redhat linux
> (2.6.32-131.0.15.el6.x86_64). This is running on one old machine, and
> thus does not really provide the liability they looking for.
> I had the thought that I could set up another server as a slave, then
> promote the slave in the event it’s necessary. I was trying I made a
> system that watches for a change in the IP number number of the server
> in dns, then downs the primary, swaps primary-secondary configs in the
> primary, restarts the primary, then does the same in the secondary. This
> actually worked on the first test from failing the primary to the
> secondary. The problem came when I stried to switch it back. When I
> tried to restart the original primary as secondary, it failed saying the
> database was corrupted.

This is completely possible if configured correctly, we do this all the
time for customers.

> There are a couple of possible solutions to this, but I’m starting to
> think that what they probably really want anyway is a Postgres server
> cluster of two servers that stay in synch with each other, and can
> simultaneously accept read and write requests. Are there any opinions
> here about the best way to set this up?

There is no "good" way to do this. There are some application specific
ways but it depends on their needs.

Joshua D. Drake


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