On Wed, 2021-04-28 at 06:34 +0000, Martin Wilck wrote: > On Wed, 2021-04-28 at 11:01 +1000, Erwin van Londen wrote: > > > > The way out of this is to chuck the array in the bin. As I mentioned > > in one of my other emails when a scenario happens as you described > > above and the array does not inform the initiator it goes against the > > SAM-5 standard. > > > > That standard shows: > > 5.14 Unit attention conditions > > 5.14.1 Unit attention conditions that are not coalesced > > Each logical unit shall establish a unit attention condition whenever > > one of the following events occurs: > > a) a power on (see 6.3.1), hard reset (see 6.3.2), logical > > unit reset (see 6.3.3), I_T nexus loss (see 6.3.4), or power loss > > expected (see 6.3.5) occurs; > > b) commands received on this I_T nexus have been cleared by > > a command or a task management function associated with another I_T > > nexus and the TAS bit was set to zero in the Control mode page > > associated with this I_T nexus (see 5.6); > > c) the portion of the logical unit inventory that consists > > of administrative logical units and hierarchical logical units has > > been changed (see 4.6.18.1); or > > d) any other event requiring the attention of the SCSI > > initiator device. > > > > Especially the I_T nexus loss under a is an important trigger. > > > > --- > > 6.3.4 I_T nexus loss > > An I_T nexus loss is a SCSI device condition resulting from: > > > > a) a hard reset condition (see 6.3.2); > > b) an I_T nexus loss event (e.g., logout) indicated by a Nexus Loss > > event notification (see 6.4); > > c) indication that an I_T NEXUS RESET task management request (see > > 7.6) has been processed; or > > d) an indication that a REMOVE I_T NEXUS command (see SPC-4) has > > been processed. > > An I_T nexus loss event is an indication from the SCSI transport > > protocol to the SAL that an I_T nexus no > > longer exists. SCSI transport protocols may define I_T nexus loss > > events. > > > > Each SCSI transport protocol standard that defines I_T nexus loss > > events should specify when those events > > result in the delivery of a Nexus Loss event notification to the SAL. > > > > The I_T nexus loss condition applies to both SCSI initiator devices > > and SCSI target devices. > > > > If a SCSI target port detects an I_T nexus loss, then a Nexus Loss > > event notification shall be delivered to > > each logical unit to which the I_T nexus has access. > > > > In response to an I_T nexus loss condition a logical unit shall take > > the following actions: > > a) abort all commands received on the I_T nexus as described in 5.6; > > b) abort all background third-party copy operations (see SPC-4) that > > are using the I_T nexus; > > c) terminate all task management functions received on the I_T nexus; > > d) clear all ACA conditions (see 5.9.5) associated with the I_T > > nexus; > > e) establish a unit attention condition for the SCSI initiator port > > associated with the I_T nexus (see 5.14 > > and 6.2); and > > f) perform any additional functions required by the applicable > > command standards. > > --- > > > > This does also mean that any underlying transport protocol issues > > like on FC or TCP for iSCSI will very often trigger aborted commands > > or UA's as well which will be picked up by the kernel/respected > > drivers. > > Thanks a lot. I'm not quite certain which of these paragraphs would > apply to the situation I had in mind (administrator remapping an > existing LUN on a storage array to a different volume). That scenario > wouldn't necessarily involve transport-level errors, or an I_T nexus > loss. 5.14.1 c) or d) might apply, is that what you meant? I was indeed mostly referring to: c) the portion of the logical unit inventory that consists of administrative logical units and hierarchical logical units has been changed (see 4.6.18.1); or d) any other event requiring the attention of the SCSI initiator device. The IT nexus status itself might not have changed but if an abstraction layer representing a totally different set of data that would most definitely fall under d. I think swapping between a volume and one of its snapshots also falls under this > > Regards > Martin >
