(A New) Persistent Reservation Question

Andrew Hisgen Andrew.Hisgen at Eng.Sun.Com
Fri Oct 27 14:05:52 PDT 2000


* 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: Roger Cummings <roger.cummings at veritas.com>
 > To: "'t10 at t10.org'" <t10 at t10.org>
 > Subject: RE: (A New) Persistent Reservation Question
 > Date: Fri, 27 Oct 2000 16:30:00 -0400
 > MIME-Version: 1.0
 > X-Message-Number: 1383
 >
 > * From the T10 Reflector (t10 at t10.org), posted by:
 > * Roger Cummings <roger.cummings at veritas.com>
 > *
 > Gerry,
 >
 > Thanks for the clarification. In that case, I'd put forward the following
 > replacement for the 6th para of 5.5.3.5 which I'd contend is significantly
 > clearer (George Penokie helped with this wording in a private thread,
 > although I must point out that he doesn't think that the clarification is
 > really warranted):
 >
 > "If the device server receives a PERSISTENT RESERVE OUT command with a
 > service action of RESERVE from the Initiator that holds the
 > existing reservation, and the Type and Scope in this PERSISTENT RESERVE OUT
 > command are identical to the Type and Scope of the existing reservation,
 > then the Device Server shall not make any change to the existing reservation
 > and shall return a GOOD status."
 >
 >
 > Which leaves me with a clear concern with respect to the situation that I
 > identified before. I think it makes no sense to reject a reservation from a
 > registered Initiator when that Initiator already has all of the rights to
 > the LU that it wants on the basis of an existing Registrants Only
 > reservation from some other Initiator.
 >
 > After all, if you look at Table 9, if another registered Initiator issues a
 > release in the presence of an existing reservation, then the existing
 > reservation isn't released and a GOOD status is returned. Why then if
 > another registered Initiator issues a RO reserve in the presence of an
 > existing RO reservation, isn't the existing reservation retained and GOOD
 > status returned?

I'ld like to "speak against" what appears to be a proposed change in
the previous two paragraphs.  The change is not necessary.

Thanks,
--Andrew Hisgen, PhD
Senior Staff Engineer,
Sun Microsystems

 >
 > Regards,
 >
 >
 >
 >
 >
 > Roger
 >
 > -----Original Message-----
 > From: Gerry.Houlder at seagate.com [mailto:Gerry.Houlder at seagate.com]
 > Sent: Friday, October 27, 2000 3:29 PM
 > To: t10 at t10.org
 > Subject: Re: (A New) Persistent Reservation Question
 >
 >
 > * From the T10 Reflector (t10 at t10.org), posted by:
 > * Gerry.Houlder at seagate.com
 > *
 >
 > Roger asked:
 >
 > >Is the 6th paragraph of 5.5.3.5 intended to refer ONLY to a second reserve
 > >that is IDENTICAL in type, scope and source (initiator) to an existing
 > >reservation ??
 >
 > My answer: Yes it is.
 >
 > You are correct that other initiators can inherit access from a registrants
 > only reservation, but they cannot become the owner of that reservation
 > unless the original owner (initiator) releases his reservation. This is a
 > feature, not a bug. The difference is response you have noted is an easy
 > way to tell whether you are the owner of the reservation or if another
 > initiator is.
 >
 >
 >
 >
 >
 > Roger Cummings <roger.cummings at veritas.com>@t10.org on 10/27/2000 10:49:23
 > AM
 >
 > Sent by:  owner-t10 at t10.org
 >
 >
 > To:   "'t10 at t10.org'" <t10 at t10.org>
 > cc:
 >
 > Subject:  (A New) Persistent Reservation Question
 >
 >
 > * From the T10 Reflector (t10 at t10.org), posted by:
 > * Roger Cummings <roger.cummings at veritas.com>
 > *
 > Folks,
 >
 > I have a question about the definition of Persistent Reservations in SPC-2
 > that I don't believe is covered by anything currently in 00-267r2. The
 > question is related  to the following:
 >
 > The 6th paragraph of 5.5.3.5 (with the response to Quantum #402 included)
 > says:
 >
 > "If the device server receives a PERSISTENT RESERVE OUT command with a
 > service action of RESERVE where
 > the TYPE and SCOPE are the same as the existing TYPE and SCOPE from the
 > initiator that created the persistent reservation,
 > it shall not make any change to the existing reservation and shall return a
 > GOOD status."
 >
 > I'm not sure that I can parse this sentence correctly, but at face value it
 > appears to conflict with Table 9, where any Reserve command  received where
 > the addressed LU has a reservation from a different initiator gets a
 > conflict.
 >
 > Is the 6th paragraph of 5.5.3.5 intended to refer ONLY to a second reserve
 > that is IDENTICAL in type, scope and source (initiator) to an existing
 > reservation ??
 >
 > What I'm worried about is this situation:
 >
 > 1) There's an existing Registrants Only (RO) LU reservation to LU 1 from
 > registered Initiator A.
 > 2) An identical RO LU reservation to LU 1 is received from Registered
 > Initiator B.
 >
 > can the reservation in 2) get a Good (allowed) response, per 5.5.3.5 ???
 >
 > Note the prior reservation doesn't need to change to grant B access
 > [because
 > the reservation in 1) allows Initiator B full access anyway].
 >
 > To look at this from another way, does it really make sense that the
 > reservation in 2) above gets a conflict when just about any other command
 > that Registered Initiator B sends will be allowed ?? Surely it would be
 > better, in the case where the rights granted under the new reservation
 > would
 > be IDENTICAL to the existing reservation, to allow the command and not
 > change the existing reservation (i.e. make the response allowed in the 3rd
 > column of table 9 and have a note similar to the one for Release).
 >
 > Regards,
 >
 >
 >
 >
 >
 >
 >
 > Roger Cummings
 > VERITAS Software
 >
 > roger.cummings at veritas.com
 > *
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