From mboxrd@z Thu Jan 1 00:00:00 1970 From: jiangyiwen Subject: dm-mpath: Handling SCSI-3 PR RELEASE in multi-controller environment Date: Wed, 21 Sep 2016 17:14:38 +0800 Message-ID: <57E24F7E.4030103@huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: dm-devel@redhat.com Cc: wangyibin@huawei.com, Mike Snitzer List-Id: dm-devel.ids Hi guys, I'm sorry if someone else has already asked the same question before, but here's what we are facing with generic multipath. We were evaluating SCSI-3 PR and hit the following issue: Our IPSAN has two controllers (C1/C2). Our host is connected to both controllers. So we have 2 I_T nexus. The same key is registered on each I_T nexus. When we issue SCSI-3 PR RESERE through generic multipath, the reservation will be placed on one of the controllers (say, C1). Now if we issue SCSI-3 PR RELEASE, generic multipath will select _only_ one of its paths based on user defined path selection policy. The problem is that, if the selected path leads to controller C2, which does not hold the reservation, the reservation won't be released - and what's more, since the reservation is done by the same host, the RELEASE command returns successfully. So this gives us the illusion that the reservation is released but in fact it is still there. I know that there's a user space tool mpathpersist that can handle this problem by issuing release command on all available paths, but here I am talking about doing same thing in kernel space. So my question is, is there anyone who is working on supporting SCSI-3 PR in a multiple controller environment? Please advise. Thanks in advance! Best regards, Yiwen