Subject: Re: [PATCHES] Infrastructure changes for recovery (v8)
From: Jeff Davis <pgsql@j-davis.com>
To: Simon Riggs <simon@2ndQuadrant.com>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>,
	List pgsql-patches <pgsql-patches@postgresql.org>
In-Reply-To: <1222815151.4445.1397.camel@ebony.2ndQuadrant>
References: <1222815151.4445.1397.camel@ebony.2ndQuadrant>
Content-Type: text/plain
Date: Fri, 07 Nov 2008 15:44:51 -0800
Message-Id: <1226101491.31701.29.camel@dell.linuxdev.us.dell.com>
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On Tue, 2008-09-30 at 23:52 +0100, Simon Riggs wrote:
> * optional recovery_safe_start_location parameter now provided in
> recovery.conf, to allow a consistency point to be manually defined if a
> base backup was not taken using standard pg_start/stop backup functions

If using synchronous replication, it seems like this may be useful. For
instance, if the primary server A fails (let's assume power off
failure), then you make the secondary server B the new primary and start
committing transactions, and then you want to bring A back up as a
secondary to B.

Will server A know where to start recovering from, even if many
checkpoints have happened on server B in the meantime? Is there a way to
avoid wiping A and making a new base backup?

Are the safety issues that Heikki brought up potentially solvable, or am
I asking for the impossible?

And also, what if server A is shut down cleanly? Is there any way at all
to get it into recovery mode to catch up with B, or would it require a
new base backup?

I haven't read through the entire thread, so I apologize if this
question has been answered elsewhere.

Regards,
	Jeff Davis