Re: iSCSI: same ISID

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

Eddy,

I am opposed to the suggestion that "conservative re-use" of ISIDs be
made a MUST. THis is really only required when initiators need to be
using the new T10 Reservation scheme that can be shared across initiator
ports.

For those initiators that don't care about this type of reservation,
conservative re-use is of no use and initiators may like to assign
ISID's in a per-initiator node fashion, thereby, being able to use these
ISIDs as a lookup index for the sessions on that initiator node.

Hence, I suggest that "conservative re-use" be worded as "encouraged to
use" or something to that effect, but not MUST USE.

Comments ?

Regards,
Santosh

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Subject: iSCSI: same ISID
Date:    Thu, 20 Dec 2001 13:39:27 -0500
From:   "Eddy Quicksall" <Eddy_Quicksall@ivivity.com>
To:     "ips@ece. cmu. edu (E-mail)" <ips@ece.cmu.edu>

Section 9.1.1 says:

the same ISID should be used in the Login process to multiple target
portal groups (of the same iSCSI Target or different iSCSI Targets). 
Note that the ISID RULE (2.5.3) only prohibits reuse to the same target
portal group.  It also does not "preclude" reuse to other target portal
groups.  

The principle of conservative reuse "encourages" reuse to other target
portal groups.  When a SCSI target device sees the same (InitiatorName,
ISID) pair in different sessions to different target portal groups, it
can identify the underlying SCSI Initiator Port on  each session as the
same SCSI port (in effect, it can recognize multiple paths from the same
source).

This is good but the target will still have to sort out ISID's when they
are different under the same situations named above. So, since the
target still has to have all the code to sort this out, what good is
this statement?


I think the only thing keeping us from saying you MUST use the same
ISID's is the fact that we have allowed an iSCSI Initiator to have more
than one session to the iSCSI Target Portal Group. Is that really
necessary? If not, then we could make this a MUST and simplify the
target code.
 

Eddy

-- 
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Santosh Rao
Software Design Engineer,
HP-UX iSCSI Driver Team,
Hewlett Packard, Cupertino.
email : santoshr@cup.hp.com
Phone : 408-447-3751
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