Re: Synchronization levels in SR

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Simon Riggs <simon(at)2ndQuadrant(dot)com>
Cc: Markus Wanner <markus(at)bluegap(dot)ch>, Robert Haas <robertmhaas(at)gmail(dot)com>, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Synchronization levels in SR
Date: 2010-09-07 15:43:47
Message-ID: 10926.1283874227@sss.pgh.pa.us
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Simon Riggs <simon(at)2ndQuadrant(dot)com> writes:
> On Tue, 2010-09-07 at 11:17 -0400, Tom Lane wrote:
>> We can *not* allow the slave to replay WAL ahead of what is known
>> committed to disk on the master. The only way to make that safe
>> is the compare-notes-and-ship-WAL-back approach that Robert mentioned.
>>
>> If you feel that decoupling WAL application is absolutely essential
>> to have a credible feature, then you'd better bite the bullet and
>> start working on the ship-WAL-back code.

> Why not just failover?

Guaranteed failover is another large piece we don't have.

regards, tom lane

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