Logical unit groups and optional target reset

Charles Monia cmonia at NishanSystems.com
Tue Jan 2 15:37:58 PST 2001


* From the T10 Reflector (t10 at t10.org), posted by:
* Charles Monia <cmonia at NishanSystems.com>
*
Hi Andrew:

See my comments below.

> -----Original Message-----
> From: Andrew Hisgen [mailto:Andrew.Hisgen at Eng.Sun.Com]
> Sent: Tuesday, January 02, 2001 11:48 AM
> To: Robert.Elliott at COMPAQ.com; t10 at t10.org; cmonia at NishanSystems.com
> Subject: RE: Logical unit groups and optional target reset
> 
> 
> * From the T10 Reflector (t10 at t10.org), posted by:
> * Andrew Hisgen <Andrew.Hisgen at eng.sun.com>
> *
> 
> > X-Authentication-Warning: t10.t10.org: lohmeyer set sender to 
> owner-t10 at t10.org using -f
> > From: Charles Monia <cmonia at NishanSystems.com>
> > To: "Elliott, Robert" <Robert.Elliott at COMPAQ.com>, "'t10 at t10.org'" 
> <t10 at t10.org>
> > Subject: RE: Logical unit groups and optional target reset
> > Date: Fri, 29 Dec 2000 17:27:55 -0800
> > MIME-Version: 1.0
> > X-Message-Number: 1499
> > 
> > * From the T10 Reflector (t10 at t10.org), posted by:
> > * Charles Monia <cmonia at NishanSystems.com>
> > *


> > > -----Original Message-----
> > > From: Elliott, Robert [mailto:Robert.Elliott at COMPAQ.com]
> > > Sent: Friday, December 29, 2000 2:11 PM
> > > To: 't10 at t10.org'
> > > Subject: RE: Logical unit groups and optional target reset
> > > 
> > > 
> > 
> > <material deleted>
> > 
> > > > 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.
> > > 
> > 
> > For a shared device, doesn't an LU reset have similar 
> adverse side effects
> > on other initiators?  This still leaves me wondering 
> whether or not it would
> > be better to restrict the operation altogether.
> 
> We need it to have those side-effects, when the device is wedged.
> Yes, target reset is a powerful hammer, but we need it to unwedge
> the device.  The fact that multiple initiators are affected is
> kind of beside the point when the device is wedged anyway.
> Thanks,

No argument on that score.

To me, restricting the operation means providing hooks so that only a
trusted class of initiators can perform the function.  It's a bit like
controlling access to a file so that lots of users can read it but only a
trusted few can perform a write or delete operation.

<remainder deleted>

Charles
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