Re: iSCSI: Async events - SCSI and iSCSI

[Mark Bakke <mbakke@cisco.com>]

Julian-

I'd like to see them separate for two reasons:

- iSCSI and SCSI-level events are typically orthogonal, so they
  probably won't usually end up being combined anyway.  It would
  be simpler for both the target and the initiator to not attempt
  to combine them.

- Since the SCSI-level events use the data portion of the message
  for sense data, that leave iSCSI events without any way to send
  data of their own if there is a possibility of combining the
  two.  By keeping them separate, iSCSI could use the data portion
  for text keys.  In fact, Parameters 1, 2, and 3 might have been
  easier to describe had they been communicated using text keys;
  the processing of async messages is not a performance-critical
  thing anyway.

That's about it.  A target could send both in one message, but since
the desire to do this is probably an end case (a small percentage
of async messages might combine both), there's no reason why we
can't just have the target send two messages, and we end up with
a simpler, and for iSCSI events, more flexible, implementation for
both the initiator and target.

Anyway, I think that if we are going for a clear separation between
SCSI and iSCSI events, that it's even clearer if they are always
sent in separate messages.

Thanks,

Mark

Julian Satran wrote:
> 
> Mark,
> 
> As far as I recall it is not by chance. When we decided to go for a clear
> separation of SCSI and iSCSI events
> I saw no reason why a target will not want to send both, if it had them, in
> one message.
> Is there something I am missing? Obviously this runs against your later
> request for text async messages.
> 
> Julo
> 
> Mark Bakke <mbakke@cisco.com>@ece.cmu.edu on 05-09-2001 23:09:12
> 
> Please respond to Mark Bakke <mbakke@cisco.com>
> 
> Sent by:  owner-ips@ece.cmu.edu
> 
> To:   IPS <ips@ece.cmu.edu>
> cc:
> Subject:  iSCSI: Async events - SCSI and iSCSI
> 
> Julian-
> 
> I was looking at Async Message some more, and noticed that there
> is nothing to stop a target from sending a message that includes
> both iSCSI and SCSI events, since each of these are communicated
> with a different set of fields.  I would guess that this is not
> what is intended, and that the target ought to send one or the other.
> 
> Can we add some text to say:
> 
>    A target may send this message as either a SCSI Event or an
>    iSCSI Event, but not both.  Either the SCSI Event or iSCSI
>    Event field MUST be zero.
> 
> --
> Mark A. Bakke
> Cisco Systems
> mbakke@cisco.com
> 763.398.1054

-- 
Mark A. Bakke
Cisco Systems
mbakke@cisco.com
763.398.1054