RE: iSCSI Autosense Consensus, Connection next steps

["Douglas Otis" <dotis@sanlight.net>]

> -----Original Message-----
> From: owner-ips@ece.cmu.edu [mailto:owner-ips@ece.cmu.edu]On Behalf Of
> Black_David@emc.com
> Sent: Sunday, September 03, 2000 8:20 AM
> To: julian_satran@il.ibm.com; ips@ece.cmu.edu
> Cc: Black_David@emc.com
> Subject: iSCSI Autosense Consensus, Connection next steps
>
>
> > It looks like we have consensus - but the chairmen have the call.
>
> Indeed we do, and I apologize for the delay, due to an inability to
> get connected.
>
> First, on Autosense, I believe that rough consensus exists for
> iSCSI to require Autosense.  I have seen only one objection;
> If anyone other than Doug Otis disagrees with this, please
> say so on the list.

I am in favor of removing the A bit to control Autosense.  I do not disagree
with respect to that change.  The only reason for having an Autosense option
is to support legacy applications.  As things like tape drives, loaders,
etc, use untagged CA environments without suffering limitations even in a
packet mode, to preserve the application (as you would not want to bit
fiddle the CDBs within the client side drivers) allowing lack of automatic
sense *data* at the adapter may provide a solution.  It would not violate
SAM-2.  Although you certainly can enforce interface compliance, you have
less ability to enforce application compliance sitting  above a SCSI API
that does not make decisions enabling ACA. Microsoft assumes the SCSI
interface is SCSI-II as example.

As network based SCSI is likely to introduce multiple initiators into the
picture normally occupied by a single adapter, CA still provides untagged
protection for this sloth equipment.  The legacy application would not have
knowledge of this limitation and so the option was on the wrong side of the
interface.  There is no need for any option if a back door is desired and no
sense data does not cause an error within the client side driver. (You can
always insist such is an error, but if it increases customer satisfaction it
may be hard to enforce.)  I suspect there are many archive applications that
will be excluded from a pure Autosense environment as it relates to a
network version of SCSI.  Archive equipment tends to have a longer life
cycle than disk drives and as such remains behind the curve with respect to
conformance to the latest versions optimized for disk drives that have a
life cycle in months.

Doug