From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932589Ab2DKQZY (ORCPT ); Wed, 11 Apr 2012 12:25:24 -0400 Received: from acsinet15.oracle.com ([141.146.126.227]:30693 "EHLO acsinet15.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932471Ab2DKQZX (ORCPT ); Wed, 11 Apr 2012 12:25:23 -0400 To: Mike Snitzer Cc: Vivek Goyal , Jens Axboe , linux kernel mailing list , martin.petersen@oracle.com Subject: Re: [RFC PATCH] block: Change default IO scheduler to deadline except SATA From: "Martin K. Petersen" Organization: Oracle References: <20120410133708.GE21801@redhat.com> <4F843C17.5050004@kernel.dk> <20120410142148.GG21801@redhat.com> <20120410151042.GH21801@redhat.com> Date: Wed, 11 Apr 2012 12:25:15 -0400 In-Reply-To: (Mike Snitzer's message of "Tue, 10 Apr 2012 12:13:07 -0400") Message-ID: User-Agent: Gnus/5.110017 (No Gnus v0.17) Emacs/23.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Source-IP: ucsinet22.oracle.com [156.151.31.94] X-CT-RefId: str=0001.0A090206.4F85B06F.0024,ss=1,re=0.000,fgs=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >>>>> "Mike" == Mike Snitzer writes: Mike> I'm not aware of any discrete attribute (comparable to Mike> 'rotational' flag) that SCSI devices will advertise that indicates Mike> "I'm a raid array". Sadly, no. Mike> That said, we can have a _very_ good hint that a SCSI device is a Mike> raid array if: Mike> 1) optimal_io_size is not zero, minimum_io_size is not equal to Mike> optimal_io_size, and optimal_io_size is a multiple of Mike> minimum_io_size Unfortunately there are still a lot of arrays out there that don't export the relevant VPDs. I know there's a lot of resistance to doing stuff in the kernel that can be done in udev. But with my distro hat on we update the kernel much, much more frequently than we update udev rules. For a multitude of reasons. Also, when it comes to disk arrays we already have a significant portion of them hardwired in the kernel anyway (quirks, LUN discovery, device handlers). So I'd personally be fine with having a BLIST_ARRAY flag that we could trigger off of. -- Martin K. Petersen Oracle Linux Engineering