Mode Parameter changes and when they take effect

Kevin D Butt kdbutt at us.ibm.com
Wed Aug 6 14:04:04 PDT 2008


Formatted message: <A HREF="r0808065_f.htm">HTML-formatted message</A>

George,
Thanks.  Is there anything anywhere that states that modifying a mode 
parameter shall not or should not cause a POR?
Kevin D. Butt
SCSI & Fibre Channel Architect, Tape Firmware
MS 6TYA, 9000 S. Rita Rd., Tucson, AZ 85744
Tel: 520-799-2869 / 520-799-5280
Fax: 520-799-2723 (T/L:321)
Email address: kdbutt at us.ibm.com
http://www-03.ibm.com/servers/storage/ 
"Penokie, George" <George.Penokie at lsi.com> 
08/06/2008 01:54 PM
To
Kevin D Butt/Tucson/IBM at IBMUS, "t10 at t10.org" <t10 at t10.org>
cc
Subject
RE: Mode Parameter changes and when they take effect
Kevin,
There are some ways that an action requested in a command may be deferred. 
Those are:
1) when the command supports the IMMED bit (MODE SENSE and MODE SELECT do 
not)
2) if the command has explicit rules defined as to when a specific action 
is to take place ( Mode parameter block descriptor in the mode page 
parameters is an example of that)
3) if a specific page has explicit rules defined as to when a specific 
value is to take affect. (I know of none but I did not do an extensive 
search)
If the mode parameters you are referring to in your note do not have 
explicit rules stating that are not required to take effect until a POR 
occurs then SAM requires them to be valid on completion of the MODE SELECT 
command. In other words there is nothing special about the MODE SELECT 
command that allows an implementation to treat mode pages any different 
that any other kind of parameter data.
Bye for now, 
George Penokie 
LSI Corporation 
3033 41st St. NW 
Suite 100 
Rochester, MN 55901 
507-328-9017 
george.penokie at lsi.com 
From: owner-t10 at t10.org [mailto:owner-t10 at t10.org] On Behalf Of Kevin D 
Butt
Sent: Wednesday, August 06, 2008 2:09 PM
To: t10 at t10.org
Subject: Mode Parameter changes and when they take effect
I have a question related to Mode Parameters.  I have searched SPC-4 (and 
earlier SPC versions) and cannot find guidance about when the changes to 
mode parameters take effect.  This concern is related to configuration 
settings and differences in expectations of various vendors. 
Vendor 1 claims that any change to a mode parameter shall become effective 
immediately and should not cause a device to reboot. 
Vendor 2 claims that changes to some mode parameters require a reboot 
before they can be accomplished.  As such the device automatically 
performs a POR on completion of the Mode Select that changes one or more 
of these parameters. 
Vendor 3 also claims that changes to some mode parameters require a reboot 
before they can be accomplished.  This device,however, requires that an 
outside entity send a command to force the device to perform a POR.  The 
new values of the mode parameters are not in effect until after the POR. 
In another form of when do parameters take effect, the requested change to 
the format (or density) does not occur until a subsequent command (e.g., a 
Format, a Write from BOT, etc.). 
Is there any guidance in SPC? 
Thanks, 
Kevin D. Butt
SCSI & Fibre Channel Architect, Tape Firmware
MS 6TYA, 9000 S. Rita Rd., Tucson, AZ 85744
Tel: 520-799-2869 / 520-799-5280
Fax: 520-799-2723 (T/L:321)
Email address: kdbutt at us.ibm.com
http://www-03.ibm.com/servers/storage/ 



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