Re: iSCSI Autosense

[Ralph Weber <ralphoweber@compuserve.com>]

Douglas,

So, let's see if I understand what you are proposing:

  1) Keep the A bit
  2) Restrict usage of A=1 to those cases where the only
     Task Attribute value supported is 0 (Untagged)
  3) In all other cases the receipt of a SCSI Command packet
     with A=1 would be cause for a protocol error

That being the case, there are a couple of editorial fixes
needed at the end of 3.2.1 in draft-satran-iscsi-01.txt as well:

  a) Remove the reference to SAM-2 in the description of the
     A bit.  There is nothing in SAM-2 that will be even
     remotely helpful to the reader.
  b) Change the last sentence of the clause as follows to
     clarify the obligations of the initiator:

     "If autosense is turned off, the initiator must explicitly request
     transfer of the sense data by sending a REQUEST SENSE command as
     the first command delivered to the target after a command has
     completed with a CHECK CONDITION status."

Good grief.  For a group that prides itself on limiting the options in their
standards, you all sure do cling to them with Visegrip(TM) tenacity.

Thanks.

Ralph Weber
ENDL Texas

Douglas Otis wrote:

>
> Ralph,
>
> Perhaps I should say Mr. SCSI as I would not wish to slander obvious
> knowledge even if I may disagree. I agree ACA provides desired interlocks
> and Autosense is also highly desired. I was not concerned about disk drives
> as these products are easily found supporting these standards and represent
> no change to existing software.  Although your emulation description
> approximates ACA with CA devices, it is not as simple as not doing it at all
> in cases where it is not needed.  For the odd device that does run one
> command per nexus and where such use is not a horrific bottleneck and the
> removal of Autosense leaves the operation of the device unchanged, why not
> refuse Autosense?  Loaders, tape and every other odd widget you can imagine
> may fall into that CA category.  Mucking with ACA emulation seems wrong in
> these cases where this fig leaf is enough.  By creating an Autosense
> refusal, at least those such as yourself wishing to have a pure environment
> can enforce such desires.
>
> Doug