SPC-4 question on disconnect-reconnect mode page parameter

Bill.Martin at emulex.com Bill.Martin at emulex.com
Wed Jan 21 14:46:02 PST 2009

Formatted message: <a href="http://www.t10.org/cgi-bin/ac.pl?t=r&f=r0901211_f.htm">HTML-formatted message</a>

In looking at the disconnect-reconnect mode page in SPC4r17, the definition
The MAXIMUM BURST SIZE field indicates the maximum amount of data that the
target port shall transfer during a
single data transfer operation. This value is expressed in increments of 512
bytes (i.e., a value of one means 512
bytes, two means 1 024 bytes, etc.). The relationship, if any, between data
transfer operations and interconnect
tenancies is defined in the individual SCSI transport protocol standards. A
value of zero specifies there is no limit
on the amount of data transferred per data transfer operation.
This works for devices that formatted for data in multiples of 512 bytes per
block; however, this does not map well for devices that formatted for
Protection information and the block size is 520 bytes.  I understand that
the data transfer length can be easily compared to number of 512 byte blocks;
however, if you want to have a max burst size of 32 blocks that are 520 bytes
each then this field does not easily map to the number that you want because
33 would map to 32.49 520 byte blocks.	Was there any thought about tying
this to the block size that a storage device was formatted for?
Bill Martin
Office of Technology
Industry Standards
916 772-3658
916 765-6875 (Cell)
bill.martin at emulex.com

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