From mboxrd@z Thu Jan 1 00:00:00 1970 From: martin.petersen@oracle.com (Martin K. Petersen) Date: Mon, 28 May 2018 21:19:43 -0400 Subject: [PATCH 0/3] Provide more fine grained control over multipathing In-Reply-To: <20180525145056.GD9591@redhat.com> (Mike Snitzer's message of "Fri, 25 May 2018 10:50:56 -0400") References: <20180525125322.15398-1-jthumshirn@suse.de> <20180525130535.GA24239@lst.de> <20180525135813.GB9591@redhat.com> <20180525141211.GA25971@lst.de> <20180525145056.GD9591@redhat.com> Message-ID: Mike, I understand and appreciate your position but I still don't think the arguments for enabling DM multipath are sufficiently compelling. The whole point of ANA is for things to be plug and play without any admin intervention whatsoever. I also think we're getting ahead of ourselves a bit. The assumption seems to be that NVMe ANA devices are going to be broken--or that they will require the same amount of tweaking as SCSI devices--and therefore DM multipath support is inevitable. However, I'm not sure that will be the case. > Thing is you really don't get to dictate that to the industry. Sorry. We are in the fortunate position of being able to influence how the spec is written. It's a great opportunity to fix the mistakes of the past in SCSI. And to encourage the industry to ship products that don't need the current level of manual configuration and complex management. So I am in favor of Johannes' patches *if* we get to the point where a Plan B is needed. But I am not entirely convinced that's the case just yet. Let's see some more ANA devices first. And once we do, we are also in a position where we can put some pressure on the vendors to either amend the specification or fix their implementations to work with ANA. -- Martin K. Petersen Oracle Linux Engineering From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030790AbeE2BVh (ORCPT ); Mon, 28 May 2018 21:21:37 -0400 Received: from userp2130.oracle.com ([156.151.31.86]:43690 "EHLO userp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965355AbeE2BVe (ORCPT ); Mon, 28 May 2018 21:21:34 -0400 To: Mike Snitzer Cc: Christoph Hellwig , Johannes Thumshirn , Keith Busch , Sagi Grimberg , Hannes Reinecke , Laurence Oberman , Ewan Milne , James Smart , Linux Kernel Mailinglist , Linux NVMe Mailinglist , "Martin K . Petersen" , Martin George , John Meneghini Subject: Re: [PATCH 0/3] Provide more fine grained control over multipathing From: "Martin K. Petersen" Organization: Oracle Corporation References: <20180525125322.15398-1-jthumshirn@suse.de> <20180525130535.GA24239@lst.de> <20180525135813.GB9591@redhat.com> <20180525141211.GA25971@lst.de> <20180525145056.GD9591@redhat.com> Date: Mon, 28 May 2018 21:19:43 -0400 In-Reply-To: <20180525145056.GD9591@redhat.com> (Mike Snitzer's message of "Fri, 25 May 2018 10:50:56 -0400") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=8907 signatures=668702 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=753 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1711220000 definitions=main-1805290013 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Mike, I understand and appreciate your position but I still don't think the arguments for enabling DM multipath are sufficiently compelling. The whole point of ANA is for things to be plug and play without any admin intervention whatsoever. I also think we're getting ahead of ourselves a bit. The assumption seems to be that NVMe ANA devices are going to be broken--or that they will require the same amount of tweaking as SCSI devices--and therefore DM multipath support is inevitable. However, I'm not sure that will be the case. > Thing is you really don't get to dictate that to the industry. Sorry. We are in the fortunate position of being able to influence how the spec is written. It's a great opportunity to fix the mistakes of the past in SCSI. And to encourage the industry to ship products that don't need the current level of manual configuration and complex management. So I am in favor of Johannes' patches *if* we get to the point where a Plan B is needed. But I am not entirely convinced that's the case just yet. Let's see some more ANA devices first. And once we do, we are also in a position where we can put some pressure on the vendors to either amend the specification or fix their implementations to work with ANA. -- Martin K. Petersen Oracle Linux Engineering