RESERVE(6)/RELEASE(6) again, or the serial interpretations of SCSI-3.

scheible at vnet.ibm.com scheible at vnet.ibm.com
Mon Jun 17 14:25:33 PDT 1996


* From the SCSI Reflector, posted by:
* scheible at VNET.IBM.COM
*
In response to my RESERVE(6)/RELEASE(6) note, Bill Dallas wrote...

> A solution would be to obsolete RESERVE and
> RELEASE (6) for SCSI-3 and mandate the 10 byte
> versions for SCSI-3 devices.  This solution is
> only a part solution since it does not address
> those devices that have soft addressing
> (FCP, SCAM, etc).
>
> Persistent Reserve could be a solution for SCSI-3
> devices where the RESERVE and RELEASE commands are
> obsoleted for SCSI-3 and Persistent Reserve mandated.
>
> From my view point any solution that does not require
> the peripheral drivers to have specific knowledge
> of an inter-connect is good.

   To avoid transport layer specific items in the device drivers, I
assume that FCP would like to use PERSISTENT RESERVE/RELEASE.  However,
I assume this is a big change for SCAM.  Also, since SSA is a "slight"
modification over parallel SCSI, this is more code for SSA.  I cannot
judge the impact to SBP.

   I see that we need to change the mandates of SCSI-3 that do not
work for soft addressing schemes (FCP, SCAM), nor for large address
schemes (wide parallel SCSI, FCP, SBP. S3P).  It is an impact to use
RESERVE(6)/RELEASE(6) for narrow/wide SCSI, PERSISTENT RESERVE/RELEASE
for soft addressing (SCAM, FCP), transport layer functions for SBP
(although they could be hidden), and RESERVE(10)/RELEASE(10) for S3P
and makes the device driver people roll over in their graves (after it
kills them).

   Maybe this is a topic for the Serial Concerns meeting next month
during the X3T10 plenary week?

Any thoughts?

Thanks,
John Scheible
scheible at vnet.ibm.com




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