RE: question on reserve and release !

["YP Cheng" <ycheng@matissenetworks.com>]

> > When multiple iscsi initiators make calls to the same iscsi
> > target, the actual scsi device only sees one single scsi id
> > (that of the scsi HBA on the iscsi target machine).  This
> > would mean that different iscsi initiators sending scsi reserve
> > command will be interpreted by the scsi target as commands
> > from the same scsi initiator.

> Which in turn would mean that the implementation of the iscsi to
> parallel scsi gateway is broken.  SCSI is *not* an end to end
> protocol whose CDBs can be transparently passed through when
> changing transports.  For this example, the iscsi to scsi gateway
> either has to present multiple initiators to the target or has
> to implement the reserve and release functionality itself on
> behalf of the target (which should then not be connected externally
> via any means other than this gateway).

I'm confused by the above statements.  In a selection phase of parallel
SCSI, one does know the Host ID bit on the SCSI bus.  Hence, only one
initiator can reserve at a time.  Others gets "Reserve Conflict - Status
08".  For iSCSI, different initiators have their own respective sessions.
The iSCSI to parallel SCSI gateway can easily emulating a Host ID bit -
although it would need multiple logical SCSI busses when the number of
initiators exceeds 15 on a wide SCSI bus.

Y.P. Cheng
Chief Scientist, Matisse Networks.