[stgt] [Iscsitarget-devel] stgt does not preempt SCSI-2 reservations; may break MS Cluster Service failover

Lars Ellenberg lars.ellenberg at linbit.com
Tue Sep 8 10:56:51 CEST 2009

On Tue, Sep 08, 2009 at 07:54:55AM +0900, FUJITA Tomonori wrote:
> On Mon, 07 Sep 2009 10:16:06 +0200
> Florian Haas <florian.haas at linbit.com> wrote:
> > I am also failing to understand why the MS initiator would use the
> > SERVICE ACTION IN detour when upon initial login it just uses standard
> > INQUIRY commands and READ CAPACITY.
> Linux kernel also tries READ_CAPACITY_16 first (it doesn't if it knows
> that READ_CAPACITY_16 doesn't work with a device).
> I think that rejecting READ_CAPACITY_16 with Reservation Conflict is
> a bug. Can you try the following patch.

Being a SCSI illiterate myself,
I certainly will not argue with someone working in the SCSI field
for years about compliance with (already superseded) SCSI specs.

SCSI2 9.1.7 Reservations says
 ... READ CAPACITY ... is unaffected by _extent_ reservations.

Now, a LUN reservation is or is not an extent reservation?

Is this a bug in the target implementation, or is it a bug in the
initiator, trying a READ CAPACITY before a reservation?

If it is actually an initiator bug, we probably still need to work
around it, because it is the MS initiator, and the work around is
harmless in this case?

> I guess, if READ_CAPACITY_16 succeeds, MSCS goes forward.

Thanks, we will see where it wants to go today ;)

: Lars Ellenberg
: LINBIT | Your Way to High Availability
: DRBD/HA support and consulting http://www.linbit.com

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