From: David G Johnston <david.g.johnston@gmail.com>
To: pgsql-admin@postgresql.org
Subject: Re: 9.2 documentation/configuration question
Date: Tue, 2 Dec 2014 14:42:45 -0700 (MST)
Message-ID: <1417556565281-5828990.post@n5.nabble.com> (raw)
In-Reply-To: <547E1A3D.8040502@gmail.com>
References: <547E1A3D.8040502@gmail.com>
List-Unsubscribe: <mailto:majordomo@postgresql.org?body=unsub%20pgsql-admin>
Jay at Verizon wrote
> checkpoint_timeout = 5min #default
This impacts the primary machine only and ensures that regardless of the
lack of activity a crash will only need to REDO that last five minutes of
history since everything prior to that will already have been persisted to
the data files.
> archive_timeout=3600
This impacts how far, in time, the archive can be behind the master in a
low-volume situation. This is because only complete (16MB) WAL files are
shipped. In a low volume situation it may take several active
checkpoint_timeout periods (not to mention zero activity periods) to
generate enough data to fill up a single 16MB file.
In a low volume situation a single WAL will have multiple checkpoint
records. In a high volume situation there will be many WAL files that have
no checkpoint records. This later situation being the reason for the
"checkpoint_segments" parameter.
So the archive will never be more than 16MB behind the master but the
corresponding time period is unbounded in the absence of archive_timeout.
The master will always be up-to-date but the amount of time needed for
recovery is bounded either by time or size - which ever one comes first.
David J.
--
View this message in context: http://postgresql.nabble.com/9-2-documentation-configuration-question-tp5828964p5828990.html
Sent from the PostgreSQL - admin mailing list archive at Nabble.com.
--
Sent via pgsql-admin mailing list (pgsql-admin@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-admin
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-admin@postgresql.org
Cc: david.g.johnston@gmail.com
Subject: Re: 9.2 documentation/configuration question
In-Reply-To: <1417556565281-5828990.post@n5.nabble.com>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox