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Date: Mon, 20 Nov 2006 17:17:56 +0100
From: Markus Schiltknecht <markus@bluegap.ch>
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To: a.mitani@sra-europe.com
CC: pgsql-docs@postgresql.org, pgcluster-general@pgfoundry.org,
	bruce@momjian.us
Subject: Re: [Pgcluster-general] PostgreSQL Documentation of High Availability
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Hi,

a.mitani@sra-europe.com wrote:
> Current generation of PGCluster is a Shared-Nothing type of multi-master
> and syncronous replication system.

Thank you for pointing us to yet another very common distinction in the
clustering world: shared-nothing vs. shared-disk or even
shared-everything. We don't touch that in the current documentation. Do
we want or need to do so?

> I think that the feature of this type of replication system is as the
> 'Multi-Master Replication Using Clustering' chapter of your document.

Most probably, yes. Please note that it's not *my* document :-)  Bruce
Momjian wrote most of it, with only some hints and annoying nit-picking
from my side.

> However, Oracle RAC is a Shared-Everything type of multi-master clustering
> system. If it set up appropriately, most of these limitations would be
> improved.

Shared-Everything, really? I thought they did their own distributed
shared memory or distributed locking stuff, so it would be shared-disk.
And together with their OCFS, they would reach shared-nothing. But I
don't really know.

@pgsql-docs: I'd strongly vote for not mentioning Oracle if we don't
event want to mention proprietary products for PostgreSQL. There are
enough research or ongoing projects (even some ongoing reserch projects
;-)  ) to mention. PgCluster-II, GORDA, Slony-II or Postgres-R come to mind.

> Next generation of PGCluster (I named PGCluster-II) will be a
> Shared-Everything type of multi-master clustering system as demonstrated
> in Toronto.

Yeah, I remember that demonstration. Do you think PGCluster-II fits
what's described under 'Multi-Master Replication Using Clustering'? Do
you think we should explain Shared-Nothing vs. Shared-Disk vs.
Shared-Everything there?

Regards

Markus