Re: [storm] Plan for iSCSI work
<david.black@emc.com> Thu, 30 June 2011 20:27 UTC
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From: david.black@emc.com
To: hemal@broadcom.com, cbm@chadalapaka.com, pthaler@broadcom.com, storm@ietf.org
Date: Thu, 30 Jun 2011 16:22:31 -0400
Thread-Topic: [storm] Plan for iSCSI work
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Subject: Re: [storm] Plan for iSCSI work
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<WG chair hat off> I think use of "SHOULD" is the right approach here. </WG chair hat off> <WG chair hat on> Based on list discussion, I believe "SHOULD" is the rough consensus of the WG. </WG chair hat on> Thanks, --David ---------------------------------------------------- David L. Black, Distinguished Engineer EMC Corporation, 176 South St., Hopkinton, MA 01748 +1 (508) 293-7953 FAX: +1 (508) 293-7786 david.black@emc.com Mobile: +1 (978) 394-7754 ---------------------------------------------------- > -----Original Message----- > From: Hemal Shah [mailto:hemal@broadcom.com] > Sent: Thursday, June 30, 2011 2:09 PM > To: Mallikarjun Chadalapaka; Pat Thaler; Black, David; storm@ietf.org > Subject: RE: [storm] Plan for iSCSI work > > Thanks Mallikarjun! > > Hemal > > -----Original Message----- > From: Mallikarjun Chadalapaka [mailto:cbm@chadalapaka.com] > Sent: Thursday, June 30, 2011 11:06 AM > To: Pat Thaler; Hemal Shah; david.black@emc.com; storm@ietf.org > Subject: RE: [storm] Plan for iSCSI work > > Hi Pat, > > Thanks for flagging the inconsistency in 10.7, that's a good catch. Given > that and your/Hemal's feedback, I think turning the current MUST into a > SHOULD is probably the right resolution. That syncs them both to SHOULD. > Unless I see other comments, I will get this into the next revision. > > Thanks. > > Mallikarjun > > > -----Original Message----- > From: Pat Thaler [mailto:pthaler@broadcom.com] > Sent: Wednesday, June 29, 2011 4:03 PM > To: Mallikarjun Chadalapaka; Hemal Shah; david.black@emc.com; > storm@ietf.org > Subject: RE: [storm] Plan for iSCSI work > > Hi Malikarjun, > > 10.7 in the consolidated draft says that FastAbort is a SHOULD: > "Therefore, > both iSCSI target and initiator implementations SHOULD support FastAbort > multi-task abort semantics (Section 4.2.3.4)." > > When 4.2.3.5 saying "If an iSCSI target implementation is capable of > supporting TaskReporting=FastAbort functionality" implies that the > implementation was allowed to not implement FastAbort. You might > interpret "supporting" = (implemented and negotiated to TaskAbort) as you > say below, but "capable of supporting" still reads as implemented. When > the standard puts an if in front of that, it implies that an > implementation is > allowed to be not capable of supporting FastAbort. > > Neither of these is consistent with MUST implement for FastAbort. The > rationale for requiring FastAbort doesn't seem strong and I'd prefer that > the > inconsistency be resolved by not requiring its implementation. > > Regards, > Pat > > -----Original Message----- > From: storm-bounces@ietf.org [mailto:storm-bounces@ietf.org] On Behalf > Of Mallikarjun Chadalapaka > Sent: Wednesday, June 29, 2011 3:16 PM > To: Hemal Shah; david.black@emc.com; storm@ietf.org > Subject: Re: [storm] Plan for iSCSI work > > Hi Hemal, > > >1. The implementation of TaskReporting is required and NotUnderstood > response for TaskReporting key is not permitted > > No. Note that TaskReporting is not defined in RFC 3720. Patrick > MacArthur > proposed on this list a couple of weeks ago that we should fix this > disconnect in the consolidated draft - which I agreed with because I think > it's a good suggestion. > > >2. To enable FastAbort on a session, the negotiation of TaskReporting > key is required. > > Correct, specifically "TaskReporting=FastAbort" must be negotiated. > > >3. Only when the TaskReporting=FastAbort functionality is supported, > the protocol behavior specified in Section 4.2.3.4 is required to be > implemented and exhibited. > > If I were to attempt re-writing your idea, I would say: > > When the protocol behavior specified in Section 4.2.3.4 is implemented and > TaskReporting=FastAbort is operational on a session, then the FastAbort > functionality is supported/exhibited on that session by the > implementation. > > >a. Section 4.2.3.5: If an iSCSI target implementation is capable of > supporting > >TaskReporting=FastAbort functionality (Section 13.23). > > "Supporting" = implemented and negotiated to "TaskReporting=FastAbort". > Note that if even if an implementation has implemented this functionality > and wants to use it, it will not be able to negotiate it on any session if > it's > only communicating with a bunch of RFC 3720 implementations. > > >b. Section 4.2.2.3.3: Whenever the TaskReporting key (Section 12.23 > "Task Reporting") is negotiated to ResponseFence or FastAbort for an iSCSI > session. > >c. Section 4.2.2.3.4: Whenever the TaskReporting key (Section 13.23) > is > negotiated to ResponseFence or FastAbort for an iSCSI session. > > I don't see an issue. Note that the discussion in these two sections is > on > response fencing, not fast abort per se. > > >4. ...prefixed with some text like "Only when the > TaskReporting=FastAbort functionality is supported..". > > Please see the above responses. Your wording is vague for me, as I don't > comprehend a standalone notion of "supporting" a feature, other than > implementing a feature and negotiating the feature usage. Current RFC > 5048 > requirement is that implementation is MUST, and negotiation is MUST > (may result in the feature to be used, or not). So as such, there is > already > ample flexibility for implementations. > > I think you are restating your earlier suggestion to loosen the "MUST > implement" requirement in RFC5048. And I've already shared how I feel > about it, :) I think it would be a step in the wrong direction, when > faster > error recovery with multi-task aborts with large # of > sessions/LUs/initiators > is even more critical, due to increased consolidation in data centers. > > At this point, I think it would be good to also hear from the rest of the > list. > > Thanks. > > Mallikarjun > > > > > > >Thanks Mallikarjun! I would still like to confirm my understanding of > >what > you describe as "MUST implement, but MUST negotiate". > > > >Here is my understanding: > > > >1. The implementation of TaskReporting is required and NotUnderstood > response for TaskReporting key is not permitted based on the following > text > from RFC5048 and Section 6.2 of the consolidated draft: > > All keys defined in [RFC3720] MUST be supported by all > > compliant implementations; a NotUnderstood answer on any of > the > > [RFC3720] keys therefore MUST be considered a protocol > > error > and > > handled accordingly. > >2. To enable FastAbort on a session, the negotiation of TaskReporting > key is required. > >3. Only when the TaskReporting=FastAbort functionality is supported, > the protocol behavior specified in Section 4.2.3.4 is required to be > implemented and exhibited. There are several places in the spec that > indicate this type of conditionality. > >a. Section 4.2.3.5: If an iSCSI target implementation is capable of > supporting > >TaskReporting=FastAbort functionality (Section 13.23). > >b. Section 4.2.2.3.3: Whenever the TaskReporting key (Section 12.23 > "Task Reporting") is negotiated to ResponseFence or FastAbort for an iSCSI > session. > >c. Section 4.2.2.3.4: Whenever the TaskReporting key (Section 13.23) > is > negotiated to ResponseFence or FastAbort for an iSCSI session. > >4. If TaskReporting=FastAbort functionality is not supported, then > the > protocol behavior specified in Section 4.2.3.4 is not required to be > implemented or exhibited. If this is true, then the first sentence in > section > 4.2.3.4 is misleading and should be removed or prefixed with some text > like > "Only when the TaskReporting=FastAbort functionality is supported..". > > > >Hemal > > > > > >-----Original Message----- > >From: Mallikarjun Chadalapaka [mailto:cbm@chadalapaka.com] > >Sent: Friday, June 17, 2011 3:32 PM > >To: Hemal Shah; david.black@emc.com; storm@ietf.org > >Subject: RE: [storm] Plan for iSCSI work > > > >Hi Hemal, > > > >During RFC 5048 effort, I recall we settled on the "MUST implement, but > MUST > >negotiate" formulation after some list deliberation. > > > >With plain RFC 3720 semantics, there are some multi-initiator scenarios > >where multi-task aborts could essentially lead to target deadlocks, > >waiting on initiators on third-party sessions that may never respond. > >With the "Clarified" semantics in RFC 5048, the third-party deadlocks > >aren't a problem anymore, but issuing initiator could still experience > >timeouts and escalate error recovery - depending on the number of LUs, > sessions, > >connections and tasks affected with the issued TMF. Escalated error > >recovery is usually something we want to avoid as it adds more > >delays/alerts/logs/failovers/failbacks etc. Finally, "Updated" > >semantics > in > >RFC 5048 are meant to address this timeout problem - they permit > >targets to provide accelerated responses and allow them to deal with > >book-keeping/quiescing operations in a lazy fashion (which are the real > >culprits that trigger timeouts). > > > >Given all the above, the WG settled on FastAbort as a MUST-implement. > >The "MUST negotiate" part then is to enable backwards-compatibility > >with RFC > >3720 implementations. At this point, I'd rather not loosen the > Consolidated > >iSCSI draft requirement from what it is in RFC 5048. I suggest we > >leave it the way it is. > > > >Mallikarjun > > > > > > > > > > > > > >From: Hemal Shah [mailto:hemal@broadcom.com] > >Sent: Thursday, June 09, 2011 3:57 PM > >To: Mallikarjun Chadalapaka; david.black@emc.com; storm@ietf.org > >Subject: RE: [storm] Plan for iSCSI work > > > >Thanks Mallikarjun! > > > >The way I read Section 4.1.3 of RFC5048 and Section 4.2.3.4 of the > >consolidated draft, the implementation of "FastAbort" feature is a MUST. > >From the first paragraph text from Section 4.1.3 of RFC5048, the first > >sentence mandates that all iSCSI implementation comply to this section > >but the second sentence say that the requirement in this section is > >conditional to the negotiation of "FastAbort" key. > > > >Protocol behavior defined in this section MUST be implemented by all > >iSCSI implementations complying with this document. Protocol behavior > >defined in this section MUST be exhibited by iSCSI implementations on > >an iSCSI session when they negotiate the TaskReporting (Section 9.1) > >key to "FastAbort" on that session. > > > > > >This is confusing. I think it will be better to remove the first > >sentence from 4.2.3.4 and clarify that the requirements in this section > >is conditional. I suggest rewording the first two sentences to below: > > > > iSCSI implementations may negotiate the TaskReporting (Section > >9.1) key to "FastAbort" on an iSCSI session. Protocol behavior defined > >in this section MUST be exhibited by iSCSI implementations on an iSCSI > >session when they negotiate the TaskReporting (Section 9.1) key to > >"FastAbort" on that session. > > > >Hemal > > > > > >-----Original Message----- > >From: Mallikarjun Chadalapaka [mailto:cbm@chadalapaka.com] > >Sent: Friday, May 27, 2011 5:29 PM > >To: Hemal Shah; david.black@emc.com; storm@ietf.org > >Subject: RE: [storm] Plan for iSCSI work > > > >Hi Hemal, > > > >The text in this draft came verbatim from section 4.1.3 of RFC 5048. > >There have been no changes in this area. > > > >The new text (as well as the old text) requires the TaskReporting key > >to be negotiated to "FastAbort" before the multi-task abort semantics > >can be used on an iSCSI session. > > > >Thanks. > > > >Mallikarjun > > > > > > > > > > -----Original Message----- > > From: Hemal Shah [mailto:hemal@broadcom.com] > > Sent: Friday, May 27, 2011 4:51 PM > > To: Mallikarjun Chadalapaka; david.black@emc.com; storm@ietf.org > > Subject: RE: [storm] Plan for iSCSI work > > > > Mallikarjun and David, > > > > I noticed one problematic item in the consolidated draft. This item > > is > the > > requirement to support FastAbort. This feature was already defined in > > the implementation guide, but it was optional. In this draft, it > > became a required feature MUST - see in section 4.2.3.4. > > > > Do you know why the requirement was changed in the consolidated > draft? > > > > I would like to keep the requirement optional as stated in the > > implementation guide and not break backward compatibility. > > > > Hemal > > > > -----Original Message----- > > From: storm-bounces@ietf.org [mailto:storm-bounces@ietf.org] On > > Behalf Of Mallikarjun Chadalapaka > > Sent: Thursday, May 26, 2011 6:50 PM > > To: david.black@emc.com; storm@ietf.org > > Subject: Re: [storm] Plan for iSCSI work > > > > Hi David, > > > > The list of changes you have called out are already done in the > >latest draft. I > > assume then that you are suggesting that the list itself should be > >included > > in the next revision of the draft. > > > > Here's what I recall we have done so far: > > 1) iSCSIProtocolLevel specified as "1", and added a related > >normative > > reference to iSCSI-SAM draft > > 2) Markers and related keys were removed > > 3) SPKM authentication and related keys were removed > > 4) Added a new section on responding to obsoleted keys > > 5) Have explicitly allowed initiator+target implementations > >throughout the > > text > > 6) Clarified that implementations SHOULD NOT rely on SLP-based > >discovery > > 7) Added UML diagrams, and related conventions > > > > The above is of course in addition to consolidating the different > >RFCs, and > > making the related editorial changes. > > > > Thanks. > > > > Mallikarjun > > > > > > > > > > -----Original Message----- > > From: storm-bounces@ietf.org [mailto:storm-bounces@ietf.org] On > Behalf > > Of david.black@emc.com > > Sent: Friday, May 20, 2011 2:49 PM > > To: storm@ietf.org > > Subject: [storm] Plan for iSCSI work > > > > I thought I'd offer some advance planning/warning on this, as the > > consolidated iSCSI draft (draft-ietf-storm-iscsi-cons) is large > >(over > >300 > > pages). The current plan is to run a simultaneous WG Last Call on > >both > > this > > draft and the new features draft (draft-ietf-storm-iscsi-sam) > >starting in > > mid- > > June (probably the week of June 13, after I get back from a badly > needed > > vacation). That WG Last Call will run longer than the typical > >2-week time > > period, due to the total size of the drafts, but will end by July > >5th > at > >the > > latest so that the status of the drafts and the next steps are > >known prior > > to > > the T10 (SCSI standards) meetings during the week of July 11. As > >July 11th > > is also the draft cutoff deadline for the Quebec City IETF > >meetings, revised > > draft versions may not show up until that meeting week (week of July > > 24th). > > > > This is also a good point to announce that the storm WG will meet in > > Quebec City. > > I've only requested a 1-hour session, as we get most of our work > > done > on > > the mailing list. Among the items for that meeting will be > > figuring > out > > what > > to do with the RDMA extensions draft (despite its name, > >draft-ietf-storm- > > rdmap-ext-00, it's not currently an official work item for the > >storm WG). > > > > One thing that's missing from the consolidated iSCSI draft (and is > >a reason > > why we're going to need a -03 version) is the changes that it makes > >to the > > RFCs that it consolidates. Off the top of my head, the major > >changes > >are: > > - Removal of SPKM authentication > > - Removal of the Marker appendix > > - Removal of the SHOULD requirement for SLP implementation. > > Have I missed anything significant? The summary of this will need > >to > be > > added to that draft. > > > > WG Last Call will be an opportunity (in fact the final opportunity) > > to discuss > > whether anything else should be removed from iSCSI, but there's no > need > > to wait > > - I encourage people to review both drafts and post comments > whenever > > they can. > > > > In parallel, work will get started on any iSCSI MIB changes that > >are needed. > > So far, I only see one MIB change - the iSCSIProtocolLevel from the > new > > features draft needs to be added to the MIB, probably with a > structure > > analogous to the iSCSI version support that's already in the MIB. > > > > Thanks, > > --David (storm WG co-chair) > > ---------------------------------------------------- > > David L. Black, Distinguished Engineer > > EMC Corporation, 176 South St., Hopkinton, MA 01748 > > +1 (508) 293-7953 FAX: +1 (508) 293-7786 > > david.black@emc.com Mobile: +1 (978) 394-7754 > > ---------------------------------------------------- > > > > _______________________________________________ > > storm mailing list > > storm@ietf.org > > https://www.ietf.org/mailman/listinfo/storm > > > > _______________________________________________ > > storm mailing list > > storm@ietf.org > > https://www.ietf.org/mailman/listinfo/storm > > > > > > > > > > > > > > > > > > > > _______________________________________________ > storm mailing list > storm@ietf.org > https://www.ietf.org/mailman/listinfo/storm > > > > >
- [storm] Plan for iSCSI work david.black
- Re: [storm] Plan for iSCSI work Mallikarjun Chadalapaka
- Re: [storm] Plan for iSCSI work Hemal Shah
- Re: [storm] Plan for iSCSI work Mallikarjun Chadalapaka
- Re: [storm] Plan for iSCSI work Hemal Shah
- Re: [storm] Plan for iSCSI work Mallikarjun Chadalapaka
- Re: [storm] Plan for iSCSI work Hemal Shah
- Re: [storm] Plan for iSCSI work Mallikarjun Chadalapaka
- Re: [storm] Plan for iSCSI work Pat Thaler
- Re: [storm] Plan for iSCSI work Mallikarjun Chadalapaka
- Re: [storm] Plan for iSCSI work Hemal Shah
- Re: [storm] Plan for iSCSI work david.black