On 01/24/2013 09:15 AM, 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. > To handle the case where all devices are removed then new ones are added, we will not have kernel structs or /dev/sdXs to send TURs to to find new ones. Are you thinking we would do something like have the kernel create temp structs to send TURs to LUN0/well-known-lun? Or, do you think we would have something doing scsi scans (call scsi_scan_target or scsi_scan_host) every once in a while? -- 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
