From: Bruce Momjian <bruce@momjian.us>
Message-Id: <200610251540.k9PFetj27702@momjian.us>
Subject: Re: [HACKERS] Replication documentation addition
In-Reply-To: <453F3083.6080302@bluegap.ch>
To: Markus Schiltknecht <markus@bluegap.ch>
Date: Wed, 25 Oct 2006 11:40:55 -0400 (EDT)
CC: Hannu Krosing <hannu@skype.net>,
	PostgreSQL-documentation <pgsql-docs@postgresql.org>,
	PostgreSQL-development <pgsql-hackers@postgresql.org>
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Markus Schiltknecht wrote:
> Hi,
> 
> Bruce Momjian wrote:
> > I have updated the text.  Please let me know what else I should change. 
> > I am unsure if I should be mentioning commercial PostgreSQL products in
> > our documentation.
> 
> I support your POV and vote for not including any pointers to commercial 
> extensions in the official documentation. If at all, they should go to 
> 'external-projects.sgml', where PostGIS, PgAdmin and other projects are 
> mentioned.
> 
> I can't really get excited about the exclusion of the term 
> 'replication', because it's what most people are looking for. It's a 
> well known term. Sorry if it sounded that way, but I've not meant to 
> avoid that term.

OK, I have re-added the term "replication" as appropriate.

> The newly created terms 'Query Broadcast Load Balancing' or even worse 
> 'Multi-Master Load Balancing' are more confusing than helpful, because 
> these terms do not exist. (See the googlefight in [1])

OK, renamed.

> Can we name the chapter "Fail-over, Load-Balancing and Replication 
> Options"? That would fit everything and contain the necessary buzz words.

Yes. Done, "cluster" added too.

> Also, I'm still missing Multi- vs Single-Master, which are also commonly 
> used terms.

Yea, not sure how to get those in because it somewhat confuses the
"purpose" of the solution.

> IMHO, it does not make sense to speak of a synchronous replication for a 
> 'Shared Disk Fail Over'. It's not replication, because there's no replica.

Agreed.  Modified.

> The Data Partitioning paragraph should probably mention it's close 
> relation with data partitioning across table spaces (and make the 
> differences clear).

Uh, so you I/O load with table spaces.  Uh, that seems too far a reach
to mention here.

> What you call 'Query Broadcast Load Balancing' is also a multi-master 
> replication, thus naming only the later 'Multi-Master Load Balancing' 
> misleading.

Renamed.

> I'd propose to add a subsection 'Synchronous, Multi-Master Replication' 
> and explain the different possibilities on how to do that:
> 
> * Query-Based
> * with 2PC
> * Distributed SHMEM
> * (perhaps mention the optimized Postgres-R algorithm ;-)
> 
> What you called 'Single-Query Clustering' is probably better known as 
> 'Parallel Query Execution'. It can be combined with all types of 
> replication (every combination of async / sync and Single- / 
> Multi-Master). It's maybe load balancing, but it depends on some form of 
> replication to distribute the data first.

Good term.  Added.

> I liked Chris Browns documentation in [2] which was clearer regarding 
> replication (which can be used to do fail-over, load-balancing, 
> data-partitioning or parallel query execution). I'd like to keep all 
> those things a little more separate to get them clear.

Please let me know how you like the new version at the ftp URL.

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

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