Transport speed capabilities

Bob.Nixon at emulex.com Bob.Nixon at emulex.com
Thu Aug 6 13:37:28 PDT 2009


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Fibre Channel definitely supports speed negotiation, and I am aware of both
storage systems and hosts that use it, and on both Fabric and Arbitrated Loop
topologies. Is there any reason that would not be relevant to the question?
   - bob
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 1:39 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.
[cid:image001.gif at 01CA16A3.6BA5F8C0]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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