From: Michael Stone <mstone+postgres@mathom.us>
To: Scott Marlowe <smarlowe@g2switchworks.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: WAL sync behaviour
Date: Thu, 10 Nov 2005 11:00:55 -0500
Message-ID: <20051110160054.GP9905@mathom.us> (raw)
In-Reply-To: <1131637958.3554.75.camel@state.g2switchworks.com>
References: <20051110133241.GA4031@uio.no>
<437355C6.4030604@archonet.com>
<20051110142535.GA4530@uio.no>
<20051110144309.GO9905@mathom.us>
<1131637958.3554.75.camel@state.g2switchworks.com>
On Thu, Nov 10, 2005 at 09:52:38AM -0600, Scott Marlowe wrote:
>Not from what I understood. Ext2 can't guarantee that your data will
>even be there in any form after a crash.
It can if you sync the data. (Which is the whole point of the WAL.)
>I believe only metadata journaling is needed though.
If you don't sync, metadata journaling doesn't do anything to guarantee
that your data will be there, so you're adding no data security in the
non-synchronous-write case. (Which is irrelevant for the WAL.)
What metadata journalling gets you is fast recovery from crashes by
avoiding a fsck. The fsck time is related to the number of files on a
filesystem--so it's generally pretty quick on a WAL partition anyway.
Mike Stone
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-performance@postgresql.org
Cc: mstone+postgres@mathom.us, smarlowe@g2switchworks.com
Subject: Re: WAL sync behaviour
In-Reply-To: <20051110160054.GP9905@mathom.us>
* 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