From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Christie Subject: Re: [PATCH RFC 0/9] [SCSI] Enhanced sense and Unit Attention handling Date: Thu, 24 Jan 2013 08:00:20 -0700 Message-ID: <51014C84.4000906@cs.wisc.edu> References: <1358526434-1173-1-git-send-email-emilne@redhat.com> <51011D2E.305@suse.de> <51014A7B.2060806@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from sabe.cs.wisc.edu ([128.105.6.20]:35313 "EHLO sabe.cs.wisc.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754549Ab3AXPBW (ORCPT ); Thu, 24 Jan 2013 10:01:22 -0500 In-Reply-To: <51014A7B.2060806@suse.de> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Hannes Reinecke Cc: Bart Van Assche , "Ewan D. Milne" , linux-scsi@vger.kernel.org On 01/24/2013 07:51 AM, Hannes Reinecke wrote: > On 01/24/2013 03:38 PM, Bart Van Assche wrote: >> On Thu, Jan 24, 2013 at 4:38 AM, Hannes Reinecke wrote: >>> As for AEN, does iSCSI _do_ AEN? I thought it got removed ... >>> >>> If it does, though, it should schedule an event on its own whenever >>> an AER >>> is received. The same goes for LLDDs with vendor-specific AENs; >>> thinking of >>> megaraid_sas here ... >> >> Let me ask this another way. SAN users expect that the LUN list at the >> initiator side gets updated automatically after a SAN configuration >> change. How should a SAN system communicate to a SCSI initiator that >> the LUN list has been changed ? Some FC SAN systems send a LIP after a >> configuration change to force the initiator to rescan LUNs. > > And thereby disrupting traffic on _ALL_ LUNs on the loop. > Really cool idea. > I know; the one vendor which does _not_ talk to us. > >> But how to inform the initiator about a LUN change for other SCSI >> protocols ? >> I'm not sure that it is even possible to report such a change via sense >> data in case a SAN user first removes all LUNs and after that change >> adds one or more LUNs. >> > The official way is indeed via UAs; most storage arrays (Hello, NetApp!) > provide a default LUN0 which is always visible. > Up to the point that some even refuse to add 'normal' disk LUNs to LUN0. > Or have the ominous 'Well-known Address' LUN to handle these kind of > issues. > > Obviously, one needs to send commands to it to even _get_ an UA back. > In SAM5 there is that QUERY ASYNCHRONOUS EVENT TMF. Could we send that periodically to lun0/well-knwon-lun if the transport supports it (iscsi will in http://tools.ietf.org/html/draft-ietf-storm-iscsi-sam-06#section-6). Whatever daemon in userspace handles these other events, could send it (we just need to add a interface) or we could add kernel code. This should not hold up Ewan's patches though.