From: Bruce Momjian <bruce@momjian.us>
Message-Id: <200611220400.kAM406q21873@momjian.us>
Subject: Re: "Clustering"
In-Reply-To: <4562C9F3.9020300@bluegap.ch>
To: Markus Schiltknecht <markus@bluegap.ch>
Date: Tue, 21 Nov 2006 23:00:06 -0500 (EST)
CC: Peter Eisentraut <peter_e@gmx.net>, pgsql-docs@postgresql.org
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Markus Schiltknecht wrote:
> Hi,
> 
> Bruce Momjian wrote:
> > Peter Eisentraut wrote:
> >> The heading "Multi-Master Replication Using Clustering" doesn't make 
> >> sense to me.  Clustering is bunching more than host together to achieve 
> >> a common goal.  Thus multimaster replication may be a way to achieve 
> >> clustering, but clustering is not a way to achieve multimaster 
> >> replication.  I don't actually see clustering defined in the 
> >> documentation.  Can someone explain the categorization?
> 
> AFAICS, clustering seems to have no clear definition within database 
> replication.

OK, new title is "Synchonous Multi-Master Replication", and the next
heading is "Asynchronous Multi-Master Replication".

> 
> > I used the term clustering to mean that the servers work closely
> > together.  This is not as true with the other items on the page that are
> > not clustering.
> 
> Why not simply call in "Multi Master Replication"? That implies 
> clustering, doesn't it?

Well, not really because of the async multi-master that is the next
item.

> 
> Perhaps you meant a Shared Nothing Cluster by referring to clustering? 
> Such a definition would make more sense.
> 
> BTW, I'm slowly beginning to accept that you don't want to mix 
> "Statement-Based Replication Middleware" with "Multi Master 
> Replication". ;-)

OK, are they mixed now?

> >> (FWIW, I think "Clustering For Parallel Query Execution" later in the 
> >> list is an appropriate use of the term.)
> 
> That reminds me of the requirement of having Multi Master Replication in 
> place to do Parallel Query Execution. Sync Multi Master Replication 
> being better, while Async Multi Master Replication obviously leads to 
> inconsistent responses, when queried in parallel. That may be acceptable 
> in certain situations.

OK, I think we have that covered now.

> Again, IMHO, "Parallel Query Execution" says everything. The word 
> 'Clustering' does not help, because it's not defined nor commonly used 
> in any helpful way (probably besides marketing).

OK, new title is Multi-Server Parallel Query Execution.  If I have just
"Parallel Query Execution", it could be multi-process parallel
query execution.

-- 
  Bruce Momjian   bruce@momjian.us
  EnterpriseDB    http://www.enterprisedb.com

  + If your life is a hard drive, Christ can be your backup. +