RE: Real application clustering in postgres.

Thanks for your inputs Laurenz Albe.

Would you please explain single-master failover solution.

Suppose we have promoted standby (replica) as master after the h/w issue at Master.
If after few hours we recovered the h/w then how we can switchback on the old primary. .

As in Oracle we have switchover method for Dataguard. How we can do in Postgres.

Thanks,

-----Original Message-----
From: Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at>
Sent: Thursday, March 5, 2020 5:37 PM
To: Daulat Ram <Daulat(dot)Ram(at)exponential(dot)com>; pgsql-general(at)lists(dot)postgresql(dot)org
Subject: Re: Real application clustering in postgres.

On Thu, 2020-03-05 at 07:45 +0000, Daulat Ram wrote:
> Is there any possibility/options to setup a real application clustering in Postgres as in Oracle we have a RAC feature.

No, and as far as I know nobody feels interested in providing it.

RAC is a complicated architecture that doesn't do much good, so most people feel that it would be a waste of time and effort.

RAC ist not really a scaling solution: because of the shared storage, you can only scale for more CPUs; I/O remains the bottleneck.

RAC is not really a high availability solution: because of the shared storage, it has a sibgle point of failure.

Today, people use shared-nothing architectures for high avaliability, like Patroni.

> What about multi-master replication in Postgres. would you please suggest how it is useful and how can setup it.

There is no support for that in core PostgreSQL.

There is a closed-source implementation that you can buy:
https://www.2ndquadrant.com/en/resources/postgres-bdr-2ndquadrant/

But multi-master replication is complicated to get right, and an applicatoin that uses it has to be specifically designed for that.
Very often a single-master failover solution is a better solution.

Yours,
Laurenz Albe
--
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