To: pgsql-admin@postgresql.org
From: Thomas Kellerer <spam_eater@gmx.net>
Subject: Re: Setting up a warm standby server - some questions
Date: Fri, 16 Jul 2010 15:06:56 +0200
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Message-ID: <i1plhg$rol$1@dough.gmane.org>
References: <i1mnd7$9gk$1@dough.gmane.org>
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In-Reply-To: <i1mnd7$9gk$1@dough.gmane.org>

Hello,


I could solve one of the questions myself :)
> I have also problems shutting down the secondary server while it is in
> "standby" (i.e. recovery) mode

This works fine when using "-m fast" instead of "-m immediate".


I would still like an answer on these questions:

> What is the recommended way to switch back to the primary, once that is
> up and running again?  
> What is the recommended way to get the secondary back into the "standby"
> mode?


As we are trying to minimize the possible data loss, I'm looking at the archive_timeout setting (I'm currently evaluating our possibilities with 8.4)

The manual at
http://www.postgresql.org/docs/current/static/continuous-archiving.html#RECOVERY-CONFIG-SETTINGS
states:

     "It is therefore unwise to set a very short archive_timeout  — it will bloat your archive storage.
     archive_timeout settings of a minute or so are usually reasonable"

But on the other hand
http://www.postgresql.org/docs/current/static/warm-standby.html
states:

   "The length of the window of data loss can be limited by use of the archive_timeout parameter, which can
   be set as low as a few seconds if required"

but kind of restrains itself right after that by stating:

   "However such low settings will substantially increase the bandwidth requirements for file shipping"


My question is: is that the bandwidth between primary and standby?

If the archive is stored on a differend harddisk (or storgae system) as the data directory, I'd reckon it wouldn't have much impact on the primary server. Or am I missing something?


Regards
Thomas