New Log page for Information Exceptions (with note)
GOP at rchvmp3.vnet.ibm.COM
Thu Mar 7 14:46:42 PST 1996
* From the SCSI Reflector, posted by:
* "George Penokie" <GOP at RCHVMP3.VNET.IBM.COM>
I received the attached comment from our drive developers. I believe
it points out several reason for NOT implementing a new log page for
information exception reporting.
Bye for now,
Subject: New Log Page and Parm for Information Exceptions
The need for such a Log parm is a bit mind boggling. I can't conceive
of a hardware or software reason why a system developer couldn't design
their code to issue a Request Sense command rather than a Log Sense
command. Either will probably cause them to redesign their software.
The other reason that this is mind boggling is that the only "Method"
this would help in is when MRIE = 6h. If a system can't issue Request
Sense commands without getting a Check Condition for some goofy
architecture reason, they shouldn't set MRIE = 6h !
When MRIE = 0h, the system is in all likelihood NOT going to go looking
for failures anyway.
When MRIE = 1h, Asynchronous Event reporting is on. Therefore Sense
Data is generated by definition.
When MRIE = 2h, 3h, 4h, and 5h = The target returns Check Condition.
Thus no problem. It is not
Thus if a system STILL wants to use these features but can't handle
asynchronous event notification, and can't handle Sense data from check
condition (highly unlikely) then this proposal looks innocuous to me.
It sure looks like a useless cost adder to me though. Especially when
folks are trying to keep the cost of SCSI down.
But if for some reason it does go through the committee we may want
to consider allowing the target to return a larger parameter. The
code/qualifier doesn't really give the whole picture with our drives.
I would suggest allowing Targets to return more bytes, if they have
them. That way we could return data as to which PFA test actually
failed to aid in failure analysis. There are only 2 qualifiers and
we have many more tests that constitute our "Information Exceptions".
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