From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: with ECARTIS (v1.0.0; list xfs); Thu, 15 Mar 2007 06:01:20 -0700 (PDT) Received: from mail.lichtvoll.de (mondschein.lichtvoll.de [194.150.191.11]) by oss.sgi.com (8.12.10/8.12.10/SuSE Linux 0.7) with ESMTP id l2FD1E6p018217 for ; Thu, 15 Mar 2007 06:01:15 -0700 Received: from localhost (dslb-084-056-119-204.pools.arcor-ip.net [84.56.119.204]) by mail.lichtvoll.de (Postfix) with ESMTP id B19D95ADEC for ; Thu, 15 Mar 2007 13:39:37 +0100 (CET) From: Martin Steigerwald Subject: Re: cache+barriers vs cache+nobarriers vs disabled cache+barriers vs disabled cache+nobarriers Date: Thu, 15 Mar 2007 13:39:30 +0100 References: <20070315092220.1B09B193FE@mail.edu.haifa.ac.il> In-Reply-To: <20070315092220.1B09B193FE@mail.edu.haifa.ac.il> MIME-Version: 1.0 Content-Type: multipart/signed; boundary="nextPart12764108.IlLcJFcpmg"; protocol="application/pgp-signature"; micalg=pgp-sha1 Content-Transfer-Encoding: 7bit Message-Id: <200703151339.36259.Martin@lichtvoll.de> Sender: xfs-bounce@oss.sgi.com Errors-to: xfs-bounce@oss.sgi.com List-Id: xfs To: linux-xfs@oss.sgi.com --nextPart12764108.IlLcJFcpmg Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Content-Disposition: inline Am Donnerstag 15 M=E4rz 2007 schrieb Leon Kolchinsky: > Hello All, > > > After reading http://oss.sgi.com/projects/xfs/faq.html#wcache > and some posts on the list I've got the following question: > > If I have disabled write cache on the disk (hdparm -W0 /dev/hda) and by > default FS is mounted with "barrier" enabled, Is there any taste in > enabling "barrier"(by default) because write cache is disabled anyway > or may be it's a good idea to mount with "nobarriers" in this case? Hello Leon! It is not needed to enable barriers when write cache is disabled. Enabling= =20 barriers in this case shouldn't have any visible effect I think. > I thought that "barrier" is on by default to somewhat minimize > potential dangers of enabled write cache? But if write cache is > disabled, would "barrier" option just slow down the FS performance > (which is already slowed down by "hdparm -W0 /dev/had" anyway)? I think it wouldn't slow down any more, except maybe a minimal slow down=20 due to a little bit more of code executed inside XFS. But why do you want to disable write cache in the first case? As long as=20 you are using 2.6.17.7 or later you can safely enable barriers and and=20 write cache. At least that is my experience upto 2.6.20.1 with old IDE=20 drivers and now since some hours on my ThinkPad T42 2.6.20.3 with libata=20 drivers. With write barriers XFS and enabled write cache, XFS will not be as fast=20 as without write barriers and with enabled write cache - which is the=20 unsafe combination -, but it will still be faster than with disabled=20 write cache. Regards, --=20 Martin 'Helios' Steigerwald - http://www.Lichtvoll.de GPG: 03B0 0D6C 0040 0710 4AFA B82F 991B EAAC A599 84C7 --nextPart12764108.IlLcJFcpmg Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) iD8DBQBF+T6ImRvqrKWZhMcRAq3ZAJwKXM5jZFwQYMzp3nUN5vqmCRkehwCeL8VF WgwkoRpR/gI3Dx2DNoH1RCU= =QpPo -----END PGP SIGNATURE----- --nextPart12764108.IlLcJFcpmg--