Message-ID: <4D74FDEC.5040406@enterprisedb.com>
Date: Mon, 07 Mar 2011 17:46:52 +0200
From: Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>
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To: Andrew Dunstan <andrew@dunslane.net>
CC: Aidan Van Dyk <aidan@highrise.ca>, Simon Riggs <simon@2ndquadrant.com>,
	pgsql-hackers@postgresql.org
Subject: Re: Re: [COMMITTERS] pgsql: Efficient transaction-controlled
	synchronous replication.
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On 07.03.2011 17:03, Andrew Dunstan wrote:
> This is about expectations. The thing that worries me is that the use of
> this term might cause some people NOT to use 2PC because they think they
> are getting an equivalent guarantee, when in fact they are not. And
> that's hardly unreasonable. Here for example is what wikipedia says
> <http://en.wikipedia.org/wiki/Replication_%28computer_science%29>:
>
> Synchronous replication - guarantees "zero data loss" by the means
> of atomic write operation, i.e. write either completes on both sides
> or not at all. Write is not considered complete until
> acknowledgement by both local and remote storage.

Hmm, I've read that wikipedia definition before, but the "atomic" part 
never caught my eye. You do get zero data loss with what we have; if a 
meteor strikes the master, no acknowledged transaction is lost. I find 
that definition a bit confusing.

-- 
   Heikki Linnakangas
   EnterpriseDB   http://www.enterprisedb.com