Subject: Re: iSCSI: Require iSCSI to use packet formats similar to FC, etc ??

From: [email-masked]
Date: Fri, 27 Apr 2001 13:21:47 +0300

It doesn't add too much (as Robert had so many misgiving about the
performance statements).
I could not find any other two SCSI transports that have similar formats
(even on serial buses - SBP, SST and FCP are
very dissimilar).  As for gateway - remapping is the least of their issues
- state is the major one and we went a long way to minimize this for the
only other relevant serial-SCSI protocol - FCP.  I don't see why we should
make this a requirement.

Julo

"KRUEGER,MARJORIE (HP-Roseville,ex1)" <[email-masked]> on
27/04/2001 02:18:21

Please respond to "KRUEGER,MARJORIE (HP-Roseville,ex1)"
      <[email-masked]>

To:   "Ips Reflector (E-mail)" <[email-masked]>
cc:
Subject:  iSCSI: Require iSCSI to use packet formats similar to FC, etc??

Robert Snively proposes that the iSCSI Requirements document include the
following requirement WRT gateway devices:

   iSCSI MUST use packet formats similar to the common
   packet formats used by other packetized SCSI protocols where
   possible to allow both simple bridging gateways and more
   sophisticated translating gateways.

Comments?

Marjorie Krueger
Networked Storage Architecture
Networked Storage Solutions Org.
Hewlett-Packard
tel: +1 916 785 2656
fax: +1 916 785 0391
email: [email-masked]

---

From: Stephen Bailey <[email-masked]>
Date: Fri, 27 Apr 2001 15:51:55 -0400

> SST and FCP are very dissimilar

Actually, SST and FCP are deliberately virtually identical.  The SST
status PDU is identical to FCP's.  The SST command PDU is FCP's with
the transfer length removed (it's already in another piece of the ST
PDU which carries the SST command PDU).

I did that so that I wouldn't get trapped in arguments about how this,
that, or the other SAM feature is offered by SST.  I could just say,
whatever FCP does, SST does, in basically the same way.

However, with all the clout iSCSI has, I'm sure we won't have any
trouble convincing anybody that not only does iSCSI do everything the
other widely deployed network SCSI does, we fix all their bugs, and do
twice as much beyond that, too :^)

The most important thing is having a simple, one-to-one correspondence
between components of iSCSI and FCP.  The PDU layouts don't have to be
identical, but that is one way to inarguably achieve the
correspondence.  I don't see any reason why the iSCSI/FCP
correspondence shouldn't be very close.  Put another way, if the
correspondence is WORSE (more algorithmically difficult to make) than
FCP/||SCSI (which is a somewhat poor but well known correspondence)
we've totally blown it.

Steph