Re: [storm] What if a SCSI Response PDU has GOOD status and a DataSegment?

Ralph,

To answer your earlier question re: behavior of iSCSI initiators 
If the SCSI STATUS is not SCSISTAT_GOOD, Microsoft iSCSI initiator considers the data bytes included with the iSCSI PDU as sense data.  Sense data is subsequently passed to the SCSI layer with the exception of unit attention/bus reset.

Regards,

Suzanne

-----Original Message-----
From: storm-bounces@ietf.org [mailto:storm-bounces@ietf.org] On Behalf Of Julian Satran
Sent: Thursday, November 26, 2009 1:22 AM
To: Black_David@emc.com
Cc: storm@ietf.org
Subject: Re: [storm] What if a SCSI Response PDU has GOOD status and a DataSegment?

David,

The key is a good idea ... but not a great one :-)
As you certainly know there are many storage controllers (targets) on the market that support
iSCSI, FCP, iSER and even several at the same time (for different sessions usually as we and T10 never seriously considered I_T nexi on different transports).

Their SCSI layer (in the ones I know about) is completely transport oblivious so the transport is not really the layer you want to introduce status+sense for statuses other than bad (unit check).

At the SCSI level it may make a lot of sense (no pun intended either).  iSCSI will support it (without any key negotiation being required) as iSCSI does not prohibit it :-). I don't recall exactly what FCP had to say on this but I recall vaguely that there is no explicit interdiction. However some silicon vendors might be "surprised" if it happens.

Regards,
Julo

On 25/11/2009, at 19:57, <Black_David@emc.com> <Black_David@emc.com> wrote:

> [WG chair hat OFF]
> 
> Here's a little more background.  There's an open issue in T10
> about whether sending sense data with GOOD status can just be
> done, vs. whether the target ought to know in advance that
> the initiator is prepared for this.  
> 
> In keeping with the IETF advice to be "conservative in what
> is sent and liberal in what is accepted", if T10 decides not
> to address this at the SCSI level, then it'll be reasonable
> to define an iSCSI negotiation key to indicate that the
> initiator is prepared to accept (in the sense of "tolerate",
> i.e., won't cause an error or worse, rather than any promise
> to "process" or "understand") sense data for GOOD status.
> 
> In addition (as Ralph suggests), it may make sense (pun intended)
> to define this key to cover all status values, not just GOOD,
> even though only GOOD is currently under discussion in T10.
> 
> Thanks,
> --David
> 
> 
>> -----Original Message-----
>> From: storm-bounces@ietf.org [mailto:storm-bounces@ietf.org] 
>> On Behalf Of Ralph Weber
>> Sent: Tuesday, November 24, 2009 7:14 PM
>> To: storm@ietf.org
>> Subject: [storm] What if a SCSI Response PDU has GOOD status 
>> and a DataSegment?
>> 
>> One of the questions that T10 has been wrestling with lately
>> concerns a case where their equivalent of the iSCSI Response
>> PDU contains a status other than CHECK CONDITION and sense
>> data in a Data Segment.
>> 
>> What will initiators do if handed one of these beasts?
>> 
>> Note: GOOD is the current favorite doppelganger for CHECK
>> CONDITION, but BUSY et al. should be considered too when
>> thinking about what initiators might do.
>> 
>> The current belief in T10 is that initiators most likely
>> will ignore any Data Segment found in a Response PDU with
>> GOOD status. This is based on the notion that initiators
>> do not squander the extra cycles needed to validate entire
>> format of a Response PDU.
>> 
>> What do the implementers of iSCSI initiators think?
>> 
>> All the best,
>> 
>> .Ralph
>> 
>> _______________________________________________
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>> 
>> 
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