Message-ID: <453DCE3F.6010204@bluegap.ch>
Date: Tue, 24 Oct 2006 10:26:39 +0200
From: Markus Schiltknecht <markus@bluegap.ch>
User-Agent: Thunderbird 1.5.0.7 (X11/20060927)
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To: Bruce Momjian <bruce@momjian.us>
CC: PostgreSQL-documentation <pgsql-docs@postgresql.org>,
	PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: Replication documentation addition
References: <200610240420.k9O4Keq23589@momjian.us>
In-Reply-To: <200610240420.k9O4Keq23589@momjian.us>
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Hello Bruce,

Bruce Momjian wrote:
> Here is a new replication documentation section I want to add for 8.2:
> 
> 	ftp://momjian.us/pub/postgresql/mypatches/replication
> 
> Comments welcomed.

Thank you, that sounds good. It's targeted to production use and 
currently available solutions, which makes sense in the official manual.

You are explaining the sync vs. async categorization, but I sort of 
asked myself where the explanation of single vs multi-master has gone. I 
then realized, that you are talking about read-only and a "read/write 
mix of servers". Then again, you are mentioning 'Multi-Master 
Replication' as one type of replication solutions. I think we should be 
consistent in our naming. As Single- and Multi-Master are the more 
common terms among database replication experts, I'd recommend to use 
them and explain what they mean instead of introducing new names.

Along with that, I'd argue that this Single- or Multi-Master is a 
categorization as Sync vs Async. In that sense, the last chapter should 
probably be named 'Distributed-Shared-Memory Replication' or something 
like that instead of 'Multi-Master Replication', because as we know, 
there are several ways of doing Multi-Master Replication (Slony-II / 
Postgres-R, Distributed Shared Memory, 2PC in application code or the 
above mentioned 'Query Broadcast Replication', which would fall into a 
Multi-Master Replication model as well)

Also in the last chapter, instead of just saying that "PostgreSQL does 
not offer this type of replication", we could probably say that 
different projects are trying to come up with better replication 
solutions. And there are several proprietary products based on 
PostgreSQL which do solve some kinds of Multi-Master Replication. Not 
that I want to advertise for any of them, but it just sounds better than 
the current "no, we don't offer that".

As this documentation mainly covers production-quality solutions (which 
is absolutely perfect), can we document the status of current projects 
somewhere, probably in a wiki? Or at least mention them somewhere and 
point to their websites? It would help to get rid of all those rumors 
and uncertainties. Or are those intentional?

Just my two cents.

Regards

Markus