Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753841Ab0HWQzq (ORCPT ); Mon, 23 Aug 2010 12:55:46 -0400 Received: from vint.altlinux.org ([194.107.17.35]:51909 "EHLO vint.altlinux.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752331Ab0HWQzm (ORCPT ); Mon, 23 Aug 2010 12:55:42 -0400 X-Greylist: delayed 617 seconds by postgrey-1.27 at vger.kernel.org; Mon, 23 Aug 2010 12:55:41 EDT Date: Mon, 23 Aug 2010 20:45:22 +0400 From: Sergey Vlasov To: Ric Wheeler Cc: Jens Axboe , "tytso@mit.edu" , "linux-scsi@vger.kernel.org" , "linux-ide@vger.kernel.org" , "jack@suse.cz" , "linux-kernel@vger.kernel.org" , "swhiteho@redhat.com" , "linux-raid@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "dm-devel@redhat.com" , "James.Bottomley@suse.de" , "konishi.ryusuke@lab.ntt.co.jp" , Tejun Heo , "vst@vlnb.net" , Christoph Hellwig , "chris.mason@oracle.com" Subject: Re: [dm-devel] [PATCHSET block#for-2.6.36-post] block: replace barrier with sequenced flush Message-ID: <20100823164522.GA9528@atlas.home> Mail-Followup-To: Ric Wheeler , Jens Axboe , "tytso@mit.edu" , "linux-scsi@vger.kernel.org" , "linux-ide@vger.kernel.org" , "jack@suse.cz" , "linux-kernel@vger.kernel.org" , "swhiteho@redhat.com" , "linux-raid@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "dm-devel@redhat.com" , "James.Bottomley@suse.de" , "konishi.ryusuke@lab.ntt.co.jp" , Tejun Heo , "vst@vlnb.net" , Christoph Hellwig , "chris.mason@oracle.com" References: <1281616891-5691-1-git-send-email-tj@kernel.org> <20100820132214.GA6184@lst.de> <4C6E9CAF.5010202@redhat.com> <4C7269E9.9070304@kernel.org> <20100823124815.GA20095@lst.de> <4C727E96.5020801@redhat.com> <4C727F2B.6060501@fusionio.com> <4C729171.3030605@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="d6Gm4EdcadzBjdND" Content-Disposition: inline In-Reply-To: <4C729171.3030605@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1607 Lines: 42 --d6Gm4EdcadzBjdND Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Aug 23, 2010 at 11:19:13AM -0400, Ric Wheeler wrote: [...] > (2) hardware raid cards with internal buffer memory and on-card battery b= ackup=20 > (they sit in your server, disks sit in jbod like expansion shelves). Thes= e are=20 > fine if the drives in those shelves have write cache disabled. Actually some of such cards keep write cache on the drives enabled and issue FLUSH CACHE commands to the drives. E.g., 3ware 9690SA behaves like this at least with SATA drives (the FLUSH CACHE commands can be seen after enabling performance monitoring - they often end up in the "10 commands having the largest latency" table). This can actually be safe if the card waits for the FLUSH CACHE completion before making the write cache data in its battery-backed memory available for reuse (and the drive implements the FLUSH CACHE command correctly). --d6Gm4EdcadzBjdND Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) iEYEARECAAYFAkxypaIACgkQW82GfkQfsqI94QCeLiRSclQhAVlFnmFnK49Fh41s 55EAn1CXk2dhHSW/+tvscDZYwHy5ZG37 =v7Fn -----END PGP SIGNATURE----- --d6Gm4EdcadzBjdND-- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/