99-179r1 -- commands that must be serviced in foreground mode

Bill Dallas dallas at zk3.dec.com
Fri Jun 4 11:28:41 PDT 1999


* From the T10 Reflector (t10 at symbios.com), posted by:
* Bill Dallas  <dallas at zk3.dec.com>
*

Gerry wrote the following:

	"All flavors of START/STOP UNIT should be rejected. This would simplify the
	command parsing rules and eliminate the possibility of having to change the
	spindle state or power mode in the middle of a self-test."

	and

	"Some options of INQUIRY command may require disk access. Standard Inquiry
	data is OK but some types of VPD data and some implementations of Command
	Data may require disk access. Can we agree that any VPD data or Cmddt
	operations that require disk access may be rejected by the target?"


I NOT in favor of restricting these commands when in self-test for the
following:

The OS environments and SCSI are moving to a dynamic topology model.  To
track changes in the topology, the tools that SCSI provides to uniquely
ID a device are the inquiry VPD pages (pages 80 or 83).  The devices that
reject these commands while in self test can not be id'ed in a single system
or Cluster environment.  

Start/Stop commands are used in conjunction with Inquiry commands (VPD) since
some devices do not return VPD information unless spun up.  While I consider
a device that can't return VPD information for page 80 or 83 to be seriously
flawed it is something I have to live with due to history.

What would really be nice is a new command like inquiry that returns
a device's unique id no matter what, just like inquiry.  This would allow
the restriction of Start/Start and VPD info but would allow the OS to track
the topology while a device is in self-test.

Thanks
Bill

------- Replied-To Message

Date: Fri, 04 Jun 1999 14:00:42 EDT
From: Gerry_Houlder%notes.seagate.com at us9rmc.enet.dec.com (MAIL-11 Daemon)
  To: t10 at Symbios.COM
Subj: 99-179r1 -- commands that must be serviced in foreground mode

* From the T10 Reflector (t10 at symbios.com), posted by:
* Gerry_Houlder at notes.seagate.com
*
I would like to see the commands that must be serviced in foreground mode
limited to operations that do not require a disk access or have other
demands on spindle and/or actuator. This existing list nearly meets this
goal, but not quite.

All flavors of START/STOP UNIT should be rejected. This would simplify the
command parsing rules and eliminate the possibility of having to change the
spindle state or power mode in the middle of a self-test.

LOG SENSE should be rejected. In general, a disk access to a reserved disk
area is required in order to return LOG data. I would prefer not having to
interrupt the DST algorithm with other things that want disk acess.

Some options of INQUIRY command may require disk access. Standard Inquiry
data is OK but some types of VPD data and some implementations of Command
Data may require disk access. Can we agree that any VPD data or Cmddt
operations that require disk access may be rejected by the target?


*
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