On Thu, 2013-01-24 at 16:15 +0100, Hannes Reinecke wrote: > On 01/24/2013 04:00 PM, Mike Christie wrote: > > 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 <hare@xxxxxxx> 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. > > > Oh, cool. > Polling a device to figure out if we should poll it :-) > > We'd be better off sending TEST UNIT READY to it; then we should > be getting UAs regardless on the SAM version in use on the target. I believe that multipath is already sending periodic commands to devices through the different paths, to determine up-to-date path status. So, in at least some cases, we wouldn't have to do anything else. > > (Especially as some target lie about the supported version, so > they might be supporting SAM-5 without telling us ...) > > > This should not hold up Ewan's patches though. > > > Correct. > > AEN handling discussion is a different story and should be build > on top of Ewans patches. > > Cheers, > > Hannes -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
