SBC-3 Power Conditions model
roweber at IEEE.org
Wed Mar 25 06:28:30 PDT 2009
* From the T10 Reflector (t10 at t10.org), posted by:
* Ralph Weber <roweber at ieee.org>
I have a few questions about 4.17.1 in SBC-3.
Regarding the following entry in the first a,b,c list:
"b) the power consumed by the SCSI target device while
in the stopped power condition should be less than the
power consumed when the logical unit is in the active
power condition or any of the idle power conditions
(i.e., for devices that have a rotating medium, the
stopped power condition shall stop the rotating medium);"
Question: The absence of any mention of standby in the
text suggests that a device in one of the standby power
conditions can consume less power than a device in the
stopped power condition. Is this a desirable outcome?
Two paragraphs farther down the subclause there is a
list that describes the responses to a REQUEST SENSE
command if a logical unit is in an idle power condition.
The list is identical to a list in SPC-4 definition of
the REQUEST SENSE command.
Do we need the same lists in both standards?
My recollection is that past SPC revisions have omitted
discussion of REQUEST SENSE response caused by command-
induced power conditions changes, but that is not the
case in SPC-4 r18.
Do we want to go back to the former condition, or do
we want to remove the list from SBC-3?
A similar problem exists with the REQUEST SENSE responses
when the logical unit is in a standby power condition,
but the plot (as they say) thickens. In this case, SPC-4
is running half-and-half. One of the command cases than
can result in a standby power condition is mentioned, but
the other is not.
Surely, we will want to treat idle and standby in the
same way, and the responses to the above questions
should guide achieving that goal.
All the best,
* For T10 Reflector information, send a message with
* 'info t10' (no quotes) in the message body to majordomo at t10.org
More information about the T10