Transport speed capabilities

Paul Suhler Paul.Suhler at quantum.com
Thu Aug 6 13:37:56 PDT 2009


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I infer that the customers would use this to diagnose
lower-than-expected performance.  In other words, is the port running at
the (maximum) rate the customer paid for?  If it negotiated to a lower
speed, then the customer would like to fix the problem.
cheers,
Paul
___________________________________
Paul A. Suhler | Firmware Engineer | Quantum Corporation | Office:
949.856.7748 | paul.suhler at quantum.com 
________________________________
From: owner-t10 at t10.org [mailto:owner-t10 at t10.org] On Behalf Of
Gerry.Houlder at seagate.com
Sent: Thursday, August 06, 2009 12:39 PM
To: t10 at t10.org
Subject: Re: Transport speed capabilities
Hi Kevin,
A mode page or VPD page to report this for FC will not help very much.
The reason is that FC doesn't have a speed negotiation sequence like SAS
has and parallel SCSI had. A FC loop or fabric port is configured to run
at a particular speed (e.g., 2 Gb/sec or 4 Gb/sec), so the device being
attached to that port must be pre-configured to that speed or the
connection will fail entirely (e.g., the ports will probably report Loss
of Synch errors).
If you plug in the device and the connection works (e.g., login is
successful) then you can be sure that the newly plugged device is
configured for the same speed as the port. Reporting what speed you are
at is usually moot at this point. Reconfiguring either end typically
requires change in jumper settings or other "outside the scope of the
standards" process and is not done "on the fly".
I should think that a data sheet or product reference manual on a
product would list the supported interface speed options. I believe this
is the way most of the FC industry disseminates this information.
 Kevin D Butt <kdbutt at us.ibm.com>
				Kevin D Butt <kdbutt at us.ibm.com> 
				Sent by: owner-t10 at t10.org
				No Phone Info Available 
				08/06/2009 01:09 PM
To
t10 at t10.org	
cc
Subject
Transport speed capabilities	
I continue to have customers query me on the ability to report the
speeds that the hardware of our devices support over the transport. 
In SAS there is mode page 19h subpage 01h that provides 
PROGRAMMED MINIMUM PHYSICAL LINK RATE 
HARDWARE MINIMUM PHYSICAL LINK RATE 
PROGRAMMED MAXIMUM PHYSICAL LINK RATE 
HARDWARE MAXIMUM PHYSICAL LINK RATE 
For Fibre Channel I can find nothing comparable 
In ADC-3, there is the primary port log page that reports the current
operating information for the transport (covers pSCSI, SAS, FC) and
SSC-3 points to this page for use also. This does not, however, provide
the capabilities of the port. 
Is there some existing method to provide in the SCSI layer the ports
capabilities for the FC transport? 
Should there be an effort to create on if one does not already exist?
Maybe in the Protocol specific port information VPD page? 
Thanks, 
Kevin D. Butt
SCSI & Fibre Channel Architect, Tape Firmware
MS 6TYA, 9000 S. Rita Rd., Tucson, AZ 85744
Tel: 520-799-5280
Fax: 520-799-2723 (T/L:321)
Email address: kdbutt at us.ibm.com
http://www-03.ibm.com/servers/storage/
<http://www-03.ibm.com/servers/storage/&gt;  



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