pg.ddx.io  pgsql-performance@postgresql.org mailing list archive  

help / color / mirror / Atom feed
From: Bruno Wolff III <bruno@wolff.to>
To: Peter Kovacs <maxottovonstirlitz@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Carlos Moreno <moreno_pg@mochima.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Two hard drives --- what to do with them?
Date: Wed, 28 Feb 2007 21:28:46 -0600
Message-ID: <20070301032846.GA14102@wolff.to> (raw)
In-Reply-To: <b6e8f2e80702251411q5a27eb53re9c2a299b8e3880a@mail.gmail.com>
References: <45DF3B15.1070609@3times25.net>
	<200702231330.57014.josh@agliodbs.com>
	<45DF5DA9.90002@commandprompt.com>
	<45DF6154.5090205@3times25.net>
	<1d4e0c10702231425ke37a732y36e241902fe0aa55@mail.gmail.com>
	<45DF94BF.6050904@3times25.net>
	<45E0A500.1010707@commandprompt.com>
	<45E104DD.3080600@mochima.com>
	<2055.1172375931@sss.pgh.pa.us>
	<b6e8f2e80702251411q5a27eb53re9c2a299b8e3880a@mail.gmail.com>

On Sun, Feb 25, 2007 at 23:11:01 +0100,
  Peter Kovacs <maxottovonstirlitz@gmail.com> wrote:
> A related question:
> Is it sufficient to disable write cache only on the disk where pg_xlog
> is located? Or should write cache be disabled on both disks?

With recent linux kernels you may also have the option to use write
barriers instead of disabling caching. You need to make sure all of
your stacked block devices will handle it and most versions of software
raid (other than 1) won't. This won't be a lot faster, since at sync
points the OS needs to order a cache flush, but it does give the disks a chance
to reorder some commands in between flushes.



view thread (16+ messages)  latest in thread

Message-ID: <20070301032846.GA14102@wolff.to>
Permalink:  ../20070301032846.GA14102@wolff.to/
Also on:    postgresql.org/message-id/20070301032846.GA14102@wolff.to

 · 

reply
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: bruno@wolff.to, maxottovonstirlitz@gmail.com, tgl@sss.pgh.pa.us, moreno_pg@mochima.com
  Subject: Re: Two hard drives --- what to do with them?
  In-Reply-To: <20070301032846.GA14102@wolff.to>

* 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