Logical unit groups and optional target reset

Elliott, Robert Robert.Elliott at COMPAQ.com
Fri Dec 29 14:11:16 PST 2000


* From the T10 Reflector (t10 at t10.org), posted by:
* "Elliott, Robert" <Robert.Elliott at compaq.com>
*
> -----Original Message-----
> From: Charles Monia [mailto:cmonia at NishanSystems.com]
> Sent: Friday, December 22, 2000 4:01 PM
> Subject: RE: Logical unit groups and optional target reset
> 
> I believe simply categorizing such functionality as mandatory 
> or optional begs the question.
> 
> The main issue is how to limit access to mechanisms that are 
> deemed to be dangerous in certain environments. In my opinion, 
> in an open environment, use of such "dangerous" mechanisms 
> is best governed by the access control policy.

I reread the (approved) Access Controls proposal (99-245r9) 
and noticed this SAM-2 change covering this topic:

"c) a TARGET RESET task management request shall initiate a
logical unit reset as described in SAM-5.6.7 for all logical
units to which the initiator has access, and shall cause no
change to any logical units to which the initiator is
denied access. A response of FUNCTION COMPLETE shall
be returned in the absence of any other error condition."

So, Access Controls will prevent an initiator from resetting
with a logical unit to which it does not have access rights.
If the initiator can access the logical unit, a TARGET RESET 
will affect it.

> The other issue is whether mechanisms, such as terget reset, 
> are appropriate for a given transport.  In my view, the only 
> immutable requirement is to preserve the transport-independant 
> part of the semantics.  The definition of transport-specific
> side effects is best handled in the appropriate transport
> specification.

The transport-independent parts are a major part of the 
problem.  Tasks are aborted, mode pages are reset, etc. 
unexpectedly.  Based on the rule from 99-245r9, devices 
offering Access Controls can be set up to behave better.

---
PC: Robert.Elliott at compaq.com
UNIX: relliott at unixmail.compaq.com


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