Protection information is a SCSI Block command set concept.  The Fibre Channel and FCP layers just transfer bytes for the SCSI layer.  They don't know if the command they are carrying is block-based or not, what the block size is, or even what a "block" is.  Some SCSI command sets like OSD (object storage) and SSC (tapes) have totally different concepts of the granularity of media accesses than SBC (disks).  So, the Parameter field in the FCP frame header, which serves as a Relative Offset field for FCP_DATA IUs, is based on the number of bytes actually transferred (e.g., 520 bytes per block) not the amount of user data (e.g., 512 bytes per block).
 
--
Rob Elliott, elliott@hp.com
Hewlett-Packard Industry Standard Server Storage Advanced Technology
https://ecardfile.com/id/RobElliott

 

From: owner-t10@t10.org [mailto:owner-t10@t10.org] On Behalf Of Gary.Franco@emulex.com
Sent: Tuesday, June 06, 2006 11:24 AM
To: t10@t10.org
Subject: Relative offset calculation with data protection enabled

All,

 

I have been trying to find some statement in the various documents defining data protection, SPC/SBC and have yet to find anything discussing relative offset generation with a data protection enabled device or initiator.

 

Is the relative offset field still generated on 512 byte blocks and the DIF field just an opaque object that we have to deal with?

 

When a check and translate function is requested (DIF embedded in the data-in or data-out buffer) does the above still hold true?

 

If you know where I can find this information I would appreciate a reply.

 

__________________________________
Gary Franco Consultant Engineer
Emulex Network Systems
972-671-7433 Dallas Office
972-671-7435 Dallas Office Fax

720-652-6387 Longmont Colorado Office
720-494-1817 Longmont Colorado Office Fax

972-839-5694 Cell Phone

 

Today's Quote

It is not the cards you are dealt but what you do with them that counts.

-Anonymous


This message contains confidential information of Emulex Corporation intended only for listed recipients and should not be forwarded to anyone else. 

If you have received this message in error, please delete it immediately.  Thank you.