From owner-freebsd-fs@FreeBSD.ORG Tue Aug 28 10:55:45 2007 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 4CE7416A420 for ; Tue, 28 Aug 2007 10:55:45 +0000 (UTC) (envelope-from pjd@garage.freebsd.pl) Received: from mail.garage.freebsd.pl (arm132.internetdsl.tpnet.pl [83.17.198.132]) by mx1.freebsd.org (Postfix) with ESMTP id E6B9313C45E for ; Tue, 28 Aug 2007 10:55:44 +0000 (UTC) (envelope-from pjd@garage.freebsd.pl) Received: by mail.garage.freebsd.pl (Postfix, from userid 65534) id 8109E45E91; Tue, 28 Aug 2007 12:55:43 +0200 (CEST) Received: from localhost (pjd.wheel.pl [10.0.1.1]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mail.garage.freebsd.pl (Postfix) with ESMTP id 6BC4145685; Tue, 28 Aug 2007 12:55:39 +0200 (CEST) Date: Tue, 28 Aug 2007 12:54:35 +0200 From: Pawel Jakub Dawidek To: Simun Mikecin Message-ID: <20070828105435.GC36596@garage.freebsd.pl> References: <937640.78988.qm@web36613.mail.mud.yahoo.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="vEao7xgI/oilGqZ+" Content-Disposition: inline In-Reply-To: <937640.78988.qm@web36613.mail.mud.yahoo.com> User-Agent: Mutt/1.4.2.3i X-PGP-Key-URL: http://people.freebsd.org/~pjd/pjd.asc X-OS: FreeBSD 7.0-CURRENT i386 X-Spam-Checker-Version: SpamAssassin 3.0.4 (2005-06-05) on mail.garage.freebsd.pl X-Spam-Level: X-Spam-Status: No, score=-5.9 required=3.0 tests=ALL_TRUSTED,BAYES_00 autolearn=ham version=3.0.4 Cc: freebsd-fs@freebsd.org Subject: Re: zfs and BIO_FLUSH on amr(4) X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 28 Aug 2007 10:55:45 -0000 --vEao7xgI/oilGqZ+ Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Aug 28, 2007 at 03:00:44AM -0700, Simun Mikecin wrote: > Using storage on amr(4) controller with zfs revealed reduced write perfor= mance. > It seems that writing to zfs concludes with a BIO_FLUSH call to flush the= controller cache to > disk. >=20 > amr(4) can have onboard cache memory with or without battery backup. Is B= IO_FLUSH call really > needed when amr(4) is used with onboard cache memory with a battery backu= p? I don't think so. The thing is that when ZFS receives information that write is done, it should be on disk (at some point) and you battery-backed cache should ensure that. You can turn off sending BIO_FLUSH by setting vfs.zfs.cache_flush_disable to 1 (in /boot/loader.conf). BTW. How big performance drop do you see with BIO_FLUSH turned on? --=20 Pawel Jakub Dawidek http://www.wheel.pl pjd@FreeBSD.org http://www.FreeBSD.org FreeBSD committer Am I Evil? Yes, I Am! --vEao7xgI/oilGqZ+ Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.4 (FreeBSD) iD8DBQFG0/7rForvXbEpPzQRAoiqAKChXdHzJ+RneGfiy816ePHBHAiPTQCfQuLp pI3ni9NuGwxkL2/8XdYyotQ= =GcIO -----END PGP SIGNATURE----- --vEao7xgI/oilGqZ+--