Transport speed capabilities

Kevin D Butt kdbutt at us.ibm.com
Thu Aug 6 14:01:52 PDT 2009


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Gerry,
FC devices do support multiple speeds.	The FC standards provide for speed 
negotiation and devices support that negotiation.  Some devices may hard 
set the speed but other devices (mine included) allow either hard setting 
the speed or negotiating the speed.
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/ 
From:
Gerry.Houlder at seagate.com
To:
t10 at t10.org
Date:
08/06/2009 01:18 PM
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/ [attachment "pic18913.gif" deleted 
by Kevin D Butt/Tucson/IBM] 



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