Questions on XDWrite and XDRead commands

Warning: Dates in Calendar are closer than they appear. rroche at tdh.qntm.com
Tue Jun 3 12:20:20 PDT 1997


* From the SCSI Reflector (scsi at symbios.com), posted by:
* rroche at tdh.qntm.com (Warning: Dates in Calendar are closer than they appear.)
*

  In reviewing the XDWrite and XDRead commands in the SCSI-3 working draft,
  I have come across the following problems.

  If an initiator is using the XOR commands at queue depth, the drive may 
  run out of resources fairly quickly if no XDRead commands are issued.  This 
  is due to the fact that XDWrite commands result in locking of cache segments
  for retention of XOR result data.

  Is there an assumption that most (all?) initiator will reserve the unit
  or used linked commands to make the XDWrite/XDRead pair atomic?

  In addition, if two overlapping XDWrites are issues and then followed by
  an XDRead then what XOR result data should be returned?  Is this 
  undefined?

						Thanks,
						Rick
						rroche at tdh.qntm.com
*
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