Re: iSCSI: response to second login (with same ISID)

[Santosh Rao <santoshr@cup.hp.com>]

"KRUEGER,MARJORIE (HP-Roseville,ex1)" wrote:

>  Since
> persistent reservations are SCSI layer things, lets try to find a way to
> keep their implementation from forcing unnecessary limitations at the iSCSI
> layer.  The use of init. name+ISID+target name for identifying persistent
> reservations needs further discussion before we allow it to creep into iSCSI
> protocol rules.  I've very uncomfortable with treating ISID like a fixed
> address just because SCSI persistent reservations don't have a sufficient
> SCSI layer mechanism. 


A fixed port identifier of some form is a basic O.S. requirement to be
able to persistently bind the LUNs it sees to some form of device files.
This binding is based on either a physical port identifier or name (ex :
pSCSI target id, FC nport_id, FC port WWN) or in the case of logical
service delivery ports like iSCSI to a logical port identifier such as
the ISID.

A fixed address usage is not only for persistent reservation semantics.
The host O.S. SCSI stacks need *something* that allows them to
persistently bind device files to the same LUNs on each reboot. The ISID
is one form of achieving this. 



> Seems like this will force all kinds of layering
> violations into iSCSI.

Not clear why this is so. Consider the ISID as a logical port identifier
that id considered as a SCSI transport layer endpoint.

Regards,
Santosh
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