Re: [storm] iSCSI version descriptors (for SCSI SPC-4)
Mallikarjun Chadalapaka <cbm@chadalapaka.com> Wed, 22 September 2010 19:48 UTC
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From: Mallikarjun Chadalapaka <cbm@chadalapaka.com>
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Subject: Re: [storm] iSCSI version descriptors (for SCSI SPC-4)
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Hi David, Thanks for circling back to this. Your outline looks good overall, I like the proposed ability to let the relevant IETF WG choose the iSCSI version descriptors and associated semantics - based on a "pre-approved" numbering space from T10, albeit the "pre-approval" might in fact happen at the end as you say once we have the RFC numbers and an established IANA registry. I have two specific comments: 1) To be safe, I think we need one more defined value for iSCSIProtocolLevel: 0: No version claimed (legacy implementations) 1: RFC 3720+RFC 5048 (iSCSI protocol, with corrections and clarifications) 2: RFC-iSCSI-consolidated (with obsoleted markers & auth mechanisms and all other tweaks relative to previous baseline) 3: RFC-SAM-4 (with SAM-4 compliance support) 2) If the above looks reasonable, particularly the ordering (with implied superset semantics), seems to me that the iSCSIProtocolLevel key definition has to be in the RFC-iSCSI-consolidated for it to be able to claim a smaller number (as smaller numbers indicate chronological predecessors). Thanks. Mallikarjun > -----Original Message----- > From: david.black@emc.com [mailto:david.black@emc.com] > Sent: Monday, September 20, 2010 8:46 AM > To: cbm@chadalapaka.com; Frederick.Knight@netapp.com; storm@ietf.org > Cc: david.black@emc.com > Subject: iSCSI version descriptors (for SCSI SPC-4) > > It's time to come back to this topic. > > I believe that what should happen is to have SPC-4 point to an IANA registry for > all iSCSI version descriptors other than the existing "(no version claimed)" > descriptor (might be SPC-5 by the time we get all the pieces in place). The > reason for doing this is to put IETF in a position to create new version > descriptors for iSCSI without having to ask T10 to do so (although, it makes > sense to ask T10 to reflect the currently-valid version descriptors for iSCSI in > each version of SPC). > > Getting this to happen requires some work. For starters, note that the existing > 0x960 iSCSI version descriptor can be used by any version of iSCSI - "no version > claimed" means that no assumptions can be made about presence or absence of > functionality. For that reason, my personal (not as WG chair) preference is that > we create a version descriptor for RFC 3720 + RFC 5048 as reflected in the new > combined iSCSI draft, in order to provide a means for an implementation to > promise support for the corrections and clarifications in RFC 5048 - that > descriptor should also promise support for NAA iSCSI names (RFC 3980) and the > Node Architecture key (RFC 4850). Not using any iSCSI version descriptor, or > using the existing 0x960 version descriptor, doesn't declare absence of support - > the only valid inference that an application client (initiator) can make is "don't > know". We do need to get to a conclusion on whether to define this version > descriptor. > > The actual mechanics for coordinating this across IETF and T10 involve several > steps: > (1) The "iSCSIProtocolLevel" key should be defined in the consolidated iSCSI > draft, including creation of an IANA registry for its values (range: 0 - 31) and > defining the first two values: > 0 - unknown (equivalent to a NotUnderstood response to the key) > 1 - 3720 + 5048, etc., as reflected in the consolidated iSCSI draft. > I included 0 for completeness - it's not strictly necessary. This moves creation of > that key from the SAM 4/5 features update draft to the main consolidated draft > (2) The new SAM-4/5 features draft then defines the value 2 and adds it to that > IANA registry. > (3) As an interim measure, after WG last call is completed, we (that probably > means Fred and I) write a T10 proposal to create the version descriptors 0x961 > and 0x962 (corresponding to the values 1 and 2 for the "iSCSIProtocolLevel" > key). That makes both version descriptors usable, and provides an opportunity > for the (inevitable) T10 input on exactly how the values of the > "iSCSIProtocolLevel" key are specified. > (4) After the RFCs are published for both drafts (yes, I'm an optimist), another > T10 proposal then updates SPC-4 to cross-reference the IANA registry. > > Combining steps (3) and (4) at T10 would require both early creation of the IANA > registry and early assignment of the RFC numbers. It's not immediately clear to > me that this should be done - we can figure out whether/how to do this at the > time when the first T10 proposal needs to be written. > > Comments? > > Thanks, > --David > > > > -----Original Message----- > > From: Mallikarjun Chadalapaka [mailto:cbm@chadalapaka.com] > > Sent: Monday, March 08, 2010 2:06 AM > > To: 'Knight, Frederick'; Black, David; storm@ietf.org > > Subject: RE: [storm] SCSI Version Descriptors - iSCSI and SAM-5 > > > > Agreed on the SAM-5 version descriptor. I assume the new draft will > > in addition reference SAM-4. > > > > On the iSCSI version descriptions, I actually think creating a > > 3720+5048 version descriptor is a good start. As Fred says, existing > > implementations will be initially not reporting this so the initiator > > is left to other means to figure out the compliance level (and iSCSI > > provides the hooks to discern that). However, I believe this new > > version descriptor will help provide clarity down the road as existing > > implementations catch up to the standard - as opposed to leaving it > > open-ended until all implementations catch up to the SAM-5 draft (which takes > even longer to get to). > > > > So I guess my preference is to create a 3720+5048 version descriptor, > > assuming it's OK to approach T10 any time in future with a request to > > add additional milestones based on implementation feedback from the WG. > > > > Thanks. > > > > Mallikarjun > > > > > > > > > -----Original Message----- > > > From: storm-bounces@ietf.org [mailto:storm-bounces@ietf.org] On > > > Behalf Of Knight, Frederick > > > Sent: Tuesday, March 02, 2010 10:20 AM > > > To: Black_David@emc.com; storm@ietf.org > > > Subject: Re: [storm] SCSI Version Descriptors - iSCSI and SAM-5 > > > > > > I agree, we need to request a frozen SAM-5 version descriptor, and > > > see what they say. > > > > > > I'm reluctant to create a new descriptor to indicate compliance with > > > something old (3720+5048). > > > > > > All those existing implementations that support 3720+5048 will NOT > > > have that descriptor. What is an initiator to think? How will the > > > initiator tell an old compliant device that supports 3720+5048 with > > > no descriptor from the new compliant device that supports 3720+5048 > > > but has the descriptor? My fear is a host that assumes that if the > > > 3720+5048 descriptor you propose is NOT present, then the device must > NOT be 3720+5048 compliant. > > > > > > I'm reluctant to punish existing compliant devices by creating a > > > descriptor that they will not report. The horse is already out of > > > the barn, what good will it do to post a "please close the door" sign? > > > > > > We should however, request that T10 create a descriptor that > > > indicates compliance with the new SAM features draft (which > > > therefore means > > > 3720+5048+xxx; where xxx=the new SAM features RFC). If the device > > > 3720+5048+doesn't > > > report this new descriptor, then you must use iSCSI mechanisms to > > > determine if the device is 3720 only, or 3720+5048. > > > > > > Fred Knight > > > > > > -----Original Message----- > > > From: Black_David@emc.com [mailto:Black_David@emc.com] > > > Sent: Monday, March 01, 2010 5:53 PM > > > To: storm@ietf.org > > > Subject: [storm] SCSI Version Descriptors - iSCSI and SAM-5 > > > > > > <WG Chair Hat On> > > > > > > We have some interesting technical decisions to make around asking > > > for some SCSI version descriptor values. For those not familiar > > > with them, a SCSI device can return up to 8 2-byte version > > > descriptors in bytes 58-73 of standard INQUIRY data (see section > > > 6.4.2 in SPC-3 or the latest draft of SPC- 4). A version descriptor value > specifies both a standard and a revision. > > > Version descriptor values are defined by explicit action at T10; > > > this serves as an indirect control over which versions of standards > > > to which a device can claim to comply, and discourages compliance > > > with revisions that are unstable or otherwise unsuitable. T10 only > > > assigns version descriptors to drafts of standards that T10 believes to be > stable (e.g., suitable to implement from). > > > > > > The straightforward decision is that the iSCSI features update draft > > > (draft- > > > ietf-storm-iscsi-sam) will need to reference a stable version of the > > > SAM-5 standard (under development) prior to the completion of SAM-5 work > at T10. > > I > > > suggest that Fred Knight (editor of the draft) and I discuss this at > > > next week's meeting of T10 (specifically, the CAP WG in T10) in a > > > couple of weeks and bring the resulting recommendation to the storm > > > WG list and the Anaheim meeting. Based on what's in the current > > > draft of SAM-5, T10 may assign a version descriptor, or recommend > > > that we wait for some more things that are known to be inbound. > > > > > > The more interesting decision is version descriptors for iSCSI. > > > Currently, there's only a generic version descriptor value , 0x960h > > > "iSCSI (no version claimed)". There are an additional 31 descriptor > > > values available to iSCSI, and so the question to the storm WG is - what > would we like to see defined? > > > > > > I have two initial suggestions: > > > 1) I suggest asking that a version descriptor be defined for the combination > > > of RFC 3720 (iSCSI) and RFC 5048 (iSCSI corrections and clarifications) > > > to enable a device to claim that it has implemented RFC 5048. We could > > > add additional RFCs to this set, e.g., RFC 3980 for NAA names, although > > > I'm not sure that's useful to know post-login.' > > > 2) I strongly suggest *not* asking that a version descriptor be defined > > > for RFC 3720 by itself, as I'm concerned that such a descriptor would > > > serve as a (small) disincentive to implement RFC 5048. > > > Please comment on these. > > > > > > Thanks, > > > --David > > > ---------------------------------------------------- > > > David L. Black, Distinguished Engineer EMC Corporation, 176 South > > > St., Hopkinton, MA 01748 > > > +1 (508) 293-7953 FAX: +1 (508) 293-7786 > > > black_david@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] SCSI Version Descriptors - iSCSI and SAM-5 Black_David
- Re: [storm] SCSI Version Descriptors - iSCSI and … Knight, Frederick
- Re: [storm] SCSI Version Descriptors - iSCSI and … Mallikarjun Chadalapaka
- [storm] iSCSI version descriptors (for SCSI SPC-4) david.black
- Re: [storm] iSCSI version descriptors (for SCSI S… Ralph Weber
- Re: [storm] iSCSI version descriptors (for SCSI S… david.black
- Re: [storm] iSCSI version descriptors (for SCSI S… Knight, Frederick
- Re: [storm] iSCSI version descriptors (for SCSI S… david.black
- Re: [storm] iSCSI version descriptors (for SCSI S… David Harrington
- Re: [storm] iSCSI version descriptors (for SCSI S… david.black
- Re: [storm] iSCSI version descriptors (for SCSI S… Mallikarjun Chadalapaka
- Re: [storm] iSCSI version descriptors (for SCSI S… david.black
- Re: [storm] iSCSI version descriptors (for SCSI S… Mallikarjun Chadalapaka