Re: iSCSI - Immediate Logout Command PDUs

["Julian Satran" <Julian_Satran@il.ibm.com>]

Matthew,

Logout might be used for several reasons and recovery is one of them (but
also for maintenance).
It can also be used to logout a connection different than the one it is
issued on.

Unlike Login in which the the compelling reason for immediate was avoiding
deadlocks I do not see the same
compelling reason to mandate immediate always for logout.

Julo



"BURBRIDGE,MATTHEW (HP-UnitedKingdom,ex2)" <matthew_burbridge@hp.com>
@ece.cmu.edu on 17-09-2001 11:54:34

Please respond to "BURBRIDGE,MATTHEW (HP-UnitedKingdom,ex2)"
      <matthew_burbridge@hp.com>

Sent by:  owner-ips@ece.cmu.edu


To:   "'ips@ece.cmu.edu'" <ips@ece.cmu.edu>
cc:
Subject:  Immediate Logout Command PDUs



My colleagues and I have been discussing the use of the immediate bit in
the
Logout Command PDU.  We came to the conclusion that the immediate bit must
be set in the Logout Command PDU for the following reasons:-

a) Ordering of the logout PDU provides no benefits.  Ordering allows
commands received prior to be executed (non-SCSI CDBs) or delivered to the
SCSI layer (SCSI CDBs).  Even if queued the logout will probably occur
before those CDBs delivered to the SCSI layer have completed (especially,
it
the CDB takes along time to execute such as a long erase!). Also, any
application worth it's salt will wait for all responses to any commands to
be received before cleanly terminating an iSCSI session.

b) For recovery, the logout needs to be performed immediately.

c) It keeps the login and logout procedures in sync with each other.

Therefore please can you add to section 2.15 a sub section that reads:-

2.14.x I - Immediate
Logout MUST be issued as an immediate request (I=1)

Matthew Burbridge
Senior Development Engineer
NIS-Bristol
Hewlett Packard
Telnet: 312 7010
E-mail: matthewb@bri.hp.com