RE: iscsi: CRN support not required. [was :Re: [Fwd: iSCSI: items discussed at WG meeting]]

["Dave Peterson" <dap@cisco.com>]

Howdy All,
iSCSI currently has a CRN field but does not provide the appropriate text or
mechanisms for its usage.
Thus in my mind its broke in the iSCSI realm. I think the right thing to do,
given the resistance to actually
make it work, is to remove it from the spec. CRN is optional and a transport
is not required
to support it even though it does receive it.
The use of CmdSN at the target/transport level will provide the ordering
semantics, but unfortunately
will block traffic to all luns when an out of order condition occurs.

If the concept of CRN does come back around via T10, it will most likely be
in a different form
(e.g., it really should more than 1 byte for general consumption).

Dave

> -----Original Message-----
> From: owner-ips@ece.cmu.edu [mailto:owner-ips@ece.cmu.edu]On Behalf Of
> Black_David@emc.com
> Sent: Wednesday, April 03, 2002 8:57 PM
> To: hufferd@us.ibm.com; ips@ece.cmu.edu
> Subject: RE: iscsi: CRN support not required. [was :Re: [Fwd: iSCSI:
> items discussed at WG meeting]]
>
>
> > Every thing I have seen here, has nothing to do with an issue that is
> > broken in iSCSI.  I suggest that whomever wants to take it up
> with T10 do
> > so, and lets move on.  This is not a issue to be endlessly
> debated in this
> > list.
>
> I agree with John that this is not broken.  I seem to recall that CRN
> was added as something that SAM-2 had invented and hence iSCSI
> had to carry.
> Given the inconsistent state of its support and no serious request of
> the form "have to have CRN or else something really important breaks",
> I think the right thing to do is take CRN out, and reserve the field that
> carried it in case we have to put it back, especially if the argument for
> CRN involves T10 changing its definition (we should let T10 figure this
> out first).  LUN-specific mode pages for iSCSI are a non-starter, and
> if CRN requires them, iSCSI is unlikely to ever support CRN.
> Unless there's
> a pointed objection to this, Julian should take this message as an
> instruction
> to remove CRN from the iSCSI draft.
>
> The issues regarding CRN usage/behavior across FC/iSCSI need to
> get written
> up in the bridge/gateway draft that's being prepared.
>
> Thanks,
> --David
> ---------------------------------------------------
> David L. Black, Senior Technologist
> EMC Corporation, 42 South St., Hopkinton, MA  01748
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