Subject: SCSI command order issue

From: "Wang Yong Hong, Wilson" <[email-masked]>
Date: Sun, 24 Feb 2002 19:53:47 +0800

Hello,

Here I ask one question about SCSI protocol. 

I traced the linux kernel source code about SCSI module. 

In SCSI module, every SCSI command block is assigned 
one unique serial number. However this number is only 
valid before the block is returned to the SCSI middle layer.

There is no mechanism of sequence control for SCSI.
What is your opinion about the SCSI block out of order 
when they return to upper layer ? What do your people 
think about this ?

Thanks 

Wilson

---

From: [email-masked] (Brian A. Berg)
Date: Mon, 25 Feb 2002 21:52:48 +0000 (GMT)

SCSI supports Command Tagged Queueing, which allows more than 
one operation to be outstanding from an initiator.  The serial
number you mentioned could be the tag that is applied to outgoing
commands.  Assuming that both the initiator and target support and
use this feature, out-of-order responses may be received by an
initiator.
___________________________________________________________________
 Brian A. Berg            [email-masked]        Voice: 408.741.5010
 Berg Software Design                             FAX: 408.741.5234
 P.O. Box 3488         visit the Storage Cornucopia at www.bswd.com
 14500 Big Basin Way, Suite F       Consulting: SCSI/FC/SAN/storage
 Saratoga, CA 95070 USA