Persistent Reservation question

George_Penokie/Tivoli_Systems%TIVOLI_SYSTEMS at us.ibm.com George_Penokie/Tivoli_Systems%TIVOLI_SYSTEMS at us.ibm.com
Tue Nov 14 14:10:45 PST 2000


* From the T10 Reflector (t10 at t10.org), posted by:
* George_Penokie/Tivoli_Systems%TIVOLI_SYSTEMS at us.ibm.com
*
Patrick,
If I understand your question the answer is: that a single logical unit can
only have one reservation at a time and the entire logical unit has that
reservation. It makes no difference if it is a standard reservation or a
persistent reservation. So in your example initiator Bs reservation
attempts would be rejected until initiator As reservation is cleared.

In your note your make the comment: 'With 6 LUs, the 6 reservations would
have to be made by 6 different initiators.'
That is not true in that, for example, all 6 logical units could have been
reserved by  a single initiator. Any combination of initiators could
reserve any combination of logical units as long as there is only one
reservation for each logical unit.

Bye for now,
George Penokie

Dept 2C6  114-2 N212
E-Mail:    gpenokie at tivoli.com
Internal:  553-5208
External: 507-253-5208   FAX: 507-253-2880


Patrick Stirling <pms at veritas.com>@t10.org on 11/13/2000 09:56:30 PM

Sent by:  owner-t10 at t10.org


To:   t10 at t10.org
cc:
Subject:  Re: Persistent Reservation question



* From the T10 Reflector (t10 at t10.org), posted by:
* Patrick Stirling <pms at veritas.com>
*

David Ulrich asked:

>I have a question regarding the degree of mutual exclusion of RESERVE
>commands and PERSISTENT RESERVE IN/OUT commands.
>
>In the SPC-2 working draft rev. 18, section 5.5.1, page 21, the third
>paragraph states that "if a logical unit has been reserved by any RESERVE
>command and is still reserved by any initiator, all PERSISTENT RESERVE IN
>and all PERSISTENT RESERVE OUT commands shall conflict regardless of
>initiator or service action and shall terminate with a RESERVATION
>CONFLICT status".
>
>My question is, does that mean a PERSISTENT RESERVE IN/OUT command to any
>logical unit or only the logical unit that is reserved using a RESERVE
>command?  In other words, can the two different types of reservations
>co-exist as long as they have been executed by different logical units?

George_Penokie responded:
>All types of reservations are confined to a logical unit. So if you have
>6 logical units you could have 6 reservations from 6 different
> initiators.

David has an interesting question, which George hasn't answered. In both
types of reservation, only 1 initiator may reserve a LU. With 6 LUs, the 6
reservations would have to be made by 6 different initiators. The question
is, what does an LU do if initiator A has made a SCSI-2 RESERVATION and
initiator B wants to make a PERSISTENT RESERVATION? I think the answer
David is looking for is "no" - if a LU has either type or reservation set,
an attempt to set the other type by the same or another initiator should
fail. But I don't know this for sure. Can anyone answer definitively?

patrick

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