From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Garzik Subject: Re: [PATCH 5 of 8] sd: Detect non-rotational devices Date: Thu, 23 Apr 2009 10:39:41 -0400 Message-ID: <49F07DAD.7080107@garzik.org> References: <20090423105245.GX4593@kernel.dk> <49F04C71.6050304@garzik.org> <20090423113841.GK1926@parisc-linux.org> <49F06E3B.104@garzik.org> <1240495814.3514.8.camel@mulgrave.int.hansenpartnership.com> <20090423141644.GP1926@parisc-linux.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from srv5.dvmed.net ([207.36.208.214]:52724 "EHLO mail.dvmed.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757792AbZDWOjz (ORCPT ); Thu, 23 Apr 2009 10:39:55 -0400 In-Reply-To: <20090423141644.GP1926@parisc-linux.org> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Matthew Wilcox Cc: James Bottomley , "Martin K. Petersen" , Jens Axboe , rwheeler@redhat.com, snitzer@redhat.com, neilb@suse.de, dgilbert@interlog.com, linux-ide@vger.kernel.org, linux-scsi@vger.kernel.org Matthew Wilcox wrote: > On Thu, Apr 23, 2009 at 02:10:13PM +0000, James Bottomley wrote: >> I'm with Jeff on this one. We had an identically similar problem with >> REPORT LUNS, which, today is the basis of SCSI discovery. > > Yes, REPORT LUNS is quite essential. > > It's not exactly in the same category as reporting device form factor > and rotational speed. If REPORT LUNS is wrong, we're in really deep > trouble. If device form factr is wrong ... umm ... nothing much happens. > If rotational speed is wrong, we might have a suboptimal IO pattern. If the general attitude is "oh, that info might be wrong", why will app developers bother at all? It is better to return zeroes than have a decent probability of returning garbage. I value predictability much more than adopting a generalized rule to handle a few special case early adopters. > It's also fixable by udev. By that logic we should leave it to udev to handle the ata_version <= 7 stuff, since that is the early adopter special case. Jeff