Preempting in Persistent Reservations and other questions on Persistent Reservations

George Penokie gop at us.ibm.com
Wed Feb 11 08:05:20 PST 2004


* From the T10 Reflector (t10 at t10.org), posted by:
* George Penokie <gop at us.ibm.com>
*
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Burn, 

The relevant wording in 5.6.1 is: 

The time at which a reservation is established with respect to other
tasks being managed by the device server is 
vendor specific. Successful completion of a reservation command
indicates that the new reservation is established. 
A reservation may apply to some or all of the tasks in the task set
before the completion of the reservation 
command. The reservation shall apply to all tasks received by the device
server after successful completion of the 
reservation command. Any persistent reserve service action shall be
performed as a single indivisible event. 

The point is that you can compete commands that have already stared
executing if you do not return a completion status for the reservation
command until those other command(s) in process are complete. In other
words, a reservation is not in place until the completion of the
reservation command has been sent. 

Bye for now,
George Penokie

Dept 2C6  114-2 N212
E-Mail:    gop at us.ibm.com
Internal:  553-5208
External: 507-253-5208   FAX: 507-253-2880





Burn Alting <burn at goldweb.com.au> 
Sent by: owner-t10 at t10.org 


02/10/2004 04:50 PM 

To
t10 at t10.org 

cc

Subject
Preempting in Persistent Reservations and other questions on
Persistent Reservations

	





* From the T10 Reflector (t10 at t10.org), posted by:
* Burn Alting <burn at goldweb.com.au>
*
Hi Peoples,

I am implementing SCSI Persistent Reservations as per the T10/1416-D
Revision 16 draft. I noticed under Preempting reservations/registrations
the action
                "Process tasks as defined in 5.6.1; and "
in a number of situations - just before I may need to set unit
attentions.

Do I take this to mean, I am to allow any 'outstanding commands'
(tasks), which may have started execution prior to the Persistent
Reserve preempt command commencing, to complete PRIOR to setting Unit
Attentions on relevant initiators?

Also, once I complete my implementation, it would be exceedingly useful
to test it's functionality. I have some GPL code for Linux
(scsi_reserve-0.7-7.src.rpm) but it assumes one knows how to drive the
command appropriately. Are there any other tools I could use to test my
implementation?

Lastly, I noticed a posting about the possible removal of Element Scope.
Can I assume, that in the not to distant future, Persistent Reservations
will only deal with the complete LUN and no extent based scheme will be
required?


Thanks in advance
-- 
Burn Alting <burn at goldweb.com.au>

*
* For T10 Reflector information, send a message with
* 'info t10' (no quotes) in the message body to majordomo at t10.org



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<br><font size=2 face="sans-serif">Burn,</font>
<br>
<br><font size=2 face="sans-serif">The relevant wording in 5.6.1 is:</font>
<br>
<br><font size=2 face="sans-serif">The time at which a reservation is established
with respect to other tasks being managed by the device server is</font>
<br><font size=2 face="sans-serif">vendor specific. Successful completion
of a reservation command indicates that the new reservation is established.</font>
<br><font size=2 face="sans-serif">A reservation may apply to some or all
of the tasks in the task set before the completion of the reservation</font>
<br><font size=2 face="sans-serif">command. The reservation shall apply
to all tasks received by the device server after successful completion
of the</font>
<br><font size=2 face="sans-serif">reservation command. Any persistent
reserve service action shall be performed as a single indivisible event.</font>
<br>
<br><font size=2 face="sans-serif">The point is that you can compete commands
that have already stared executing if you do not return a completion status
for the reservation command until those other command(s) in process are
complete. In other words, a reservation is not in place until the completion
of the reservation command has been sent.</font>
<br><font size=2 face="sans-serif"><br>
Bye for now,<br>
George Penokie<br>
<br>
Dept 2C6 &nbsp;114-2 N212<br>
E-Mail: &nbsp; &nbsp;gop at us.ibm.com<br>
Internal: &nbsp;553-5208<br>
External: 507-253-5208 &nbsp; FAX: 507-253-2880<br>
<br>
</font>
<br>
<br>
<br>
<table width=100%>
<tr valign=top>
<td width=40%><font size=1 face="sans-serif"><b>Burn Alting <burn at goldweb.com.au&gt;</b>
</font>
<br><font size=1 face="sans-serif">Sent by: owner-t10 at t10.org</font>
<p><font size=1 face="sans-serif">02/10/2004 04:50 PM</font>
<td width=59%>
<table width=100%>
<tr>
<td>
<div align=right><font size=1 face="sans-serif">To</font></div>
<td valign=top><font size=1 face="sans-serif">t10 at t10.org</font>
<tr>
<td>
<div align=right><font size=1 face="sans-serif">cc</font></div>
<td valign=top>
<tr>
<td>
<div align=right><font size=1 face="sans-serif">Subject</font></div>
<td valign=top><font size=1 face="sans-serif">Preempting in Persistent
Reservations and other questions on &nbsp; &nbsp; &nbsp; &nbsp;Persistent
Reservations</font></table>
<br>
<table>
<tr valign=top>
<td>
<td></table>
<br></table>
<br>
<br>
<br><font size=2><tt>* From the T10 Reflector (t10 at t10.org), posted by:<br>
* Burn Alting <burn at goldweb.com.au&gt;<br>
*<br>
Hi Peoples,<br>
<br>
I am implementing SCSI Persistent Reservations as per the T10/1416-D<br>
Revision 16 draft. I noticed under Preempting reservations/registrations<br>
the action<br>
 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
"Process tasks as defined in 5.6.1; and "<br>
in a number of situations - just before I may need to set unit<br>
attentions.<br>
<br>
Do I take this to mean, I am to allow any 'outstanding commands'<br>
(tasks), which may have started execution prior to the Persistent<br>
Reserve preempt command commencing, to complete PRIOR to setting Unit<br>
Attentions on relevant initiators?<br>
<br>
Also, once I complete my implementation, it would be exceedingly useful<br>
to test it's functionality. I have some GPL code for Linux<br>
(scsi_reserve-0.7-7.src.rpm) but it assumes one knows how to drive the<br>
command appropriately. Are there any other tools I could use to test my<br>
implementation?<br>
<br>
Lastly, I noticed a posting about the possible removal of Element Scope.<br>
Can I assume, that in the not to distant future, Persistent Reservations<br>
will only deal with the complete LUN and no extent based scheme will be<br>
required?<br>
<br>
<br>
Thanks in advance<br>
-- <br>
Burn Alting <burn at goldweb.com.au&gt;<br>
<br>
*<br>
* For T10 Reflector information, send a message with<br>
* 'info t10' (no quotes) in the message body to majordomo at t10.org<br>
</tt></font>
<br>
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