Transport speed capabilities

Kevin D Butt kdbutt at us.ibm.com
Thu Aug 6 14:44:19 PDT 2009


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It could be used for that, but the main concern is knowing what they can 
configure the drive to do.  This is interesting when there are more than 
one hardware configurations of a device.  Also when a device may have been 
configured to limit the speed but then the infrastructure is upgraded to 
support a higher speed.  Then there is always the case of the library 
knowing what the drives contained in it support.
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/ 
From:
"Paul Suhler" <Paul.Suhler at quantum.com>
To:
<t10 at t10.org>
Date:
08/06/2009 02:15 PM
Subject:
RE: Transport speed capabilities
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/ 



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