Persistent Reservation and Reservation Key Uniqueness/non-uniqueness

Steve Sicola...Array Controller Engineering 522-2268 sicola at
Fri Jul 11 10:41:41 PDT 1997

* From the T10 (formerly SCSI) Reflector (t10 at, posted by:
* "Steve Sicola...Array Controller Engineering 522-2268" <sicola at>

Hey there..

Just a note about Reservation keys in a multi-host, multi-adapter/host
environment. There is no guarantee that an initiator will use the same
reservation key when registering with multiple LUNs. The implication for this
is the amount of memory this can mean to a controller (or even a shared disk to
a lesser extent) that has to kept persistently. Certainly it can be kept on 
disk, however, a good number of implementations may use some kind of 
non-volatile memory.

It would seem that two problems may exist here. The first being that for
multiple hosts that will have different reservation keys. This problem can be
alleviated by individual hosts using a single key for reserving LUNs for
itself. The second problem is that of multiple adapters per host, where the
potential for lots of different keys per adapter/host/LUN can explode the
information being kept and precludes clever compression of the reservation key

I am sure Tom Coughlan has brought this up before at the Working Group
meetings, however, I'd like to know what people think about this and whether
or not there is real merit from allowing unique keys per


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