Determining application client support for CRN.

Elliott, Robert Robert.Elliott at
Mon Sep 24 21:17:26 PDT 2001

* From the T10 Reflector (t10 at, posted by:
* "Elliott, Robert" <Robert.Elliott at>

> -----Original Message-----
> From: Santosh Rao [mailto:santoshr at]
> Sent: Monday, September 24, 2001 7:57 PM
> To: T10 Reflector
> Subject: Determining application client support for CRN.
> I've got some questions on the CRN field as defined in SAM-2 Rev 20
> Section 5.1 and the EPDC bit in the LUN Control Mode Page in 
> FCP-2. Your responses would be much appreciated.
> ...
>    * Is there any need for new SCSI transports to have a bit similar
>      the EPDC bit of FCP-2, if they are guaranteed to support the CRN
>      field in their SCSI Command encapsulation IUs from their initial
>      revs ? I ask this in the context of iscsi. I also ced that SRP
>      has chosen not to define the Protocol Specific LUN Page [which
>      would have contained something equivalent to the EPDC bit].

SRP does not support CRN.  It's garnered no adoption in FC and the
need for it is obviated by SSC-2's explicit command set for tapes
and by SPC-2's Extended Copy command which lets tapes serve
as initiators and avoid tape command ordering problems altogether.

Rob Elliott, Compaq Server Storage
Robert.Elliott at

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