Re: Synchronization levels in SR

From: Simon Riggs <simon(at)2ndQuadrant(dot)com>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Synchronization levels in SR
Date: 2010-05-25 16:59:28
Message-ID: 1274806768.6203.2237.camel@ebony
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On Tue, 2010-05-25 at 12:40 -0400, Robert Haas wrote:
> On Tue, May 25, 2010 at 12:28 PM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
> > Synchronous replication implies that a commit should wait. This wait is
> > experienced by the transaction, not by other parts of the system. If we
> > define robustness at the standby level then robustness depends upon
> > unseen administrators, as well as the current up/down state of standbys.
> > This is action-at-a-distance in its worst form.
>
> Maybe, but I can't help thinking people are going to want some form of
> this.
> The case where someone wants to do sync rep to the machine in
> the next rack over and async rep to a server at a remote site seems
> too important to ignore.

The use case of "machine in the next rack over and async rep to a server
at a remote site" *is* important, but you give no explanation as to why
that implies "per-standby" is the solution to it.

If you read the rest of my email, you'll see that I have explained the
problems "per-standby" settings would cause.

Please don't be so quick to claim it is me ignoring anything.

--
Simon Riggs www.2ndQuadrant.com

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