Mode Parameter changes and when they take effect
George.Penokie at lsi.com
Wed Aug 6 13:54:11 PDT 2008
Formatted message: <A HREF="r0808064_f.htm">HTML-formatted message</A>
There are some ways that an action requested in a command may be deferred.
1) when the command supports the IMMED bit (MODE SENSE and MODE SELECT do
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,
3033 41st St. NW
Rochester, MN 55901
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?
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
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