Logical unit groups and optional target reset
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>
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.
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.
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