Mode Sense

Eddy Quicksall Quicksall_SCSI at
Thu Jul 10 06:18:38 PDT 2008

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Thanks, (do you have saved and current reversed in your last sentence?)
Now when I re-read based on your answer I come up with this ... do you think
this is correct?
The LUN always has current and saved pages, even though it is not allowing
the initiator to save changes. If there is no distinction between current and
saved then it would follow that if the current were changed then the saved
must be changed also (in order to maintain "no distinction"). So the SP bit
must be 1 (but if none of them are saveable then nothing can be changed nor
Is there something that tells the initiator that there is "no distinction
between current and saved mode pages"?
  ----- Original Message ----- 
  From: Kevin_Marks at 
  To: Quicksall_SCSI at ; t10 at 
  Sent: Wednesday, July 09, 2008 9:56 PM
  Subject: RE: Mode Sense
  I would say, it means that current and saved are the same. You cannot
change the saved page without changing the current operating mode, therefore
you must always set the SP bit to 1, changing the current and saved page. A
bit of zero would mean changing the saved page but not the current and this
would not make sense if they were the same, hence the CC.
  From: owner-t10 at [mailto:owner-t10 at] On Behalf Of Eddy
  Sent: Wednesday, July 09, 2008 3:08 PM
  To: t10 at
  Subject: Mode Sense
  6.9 MODE SELECT(6) command
  . . .
  A save pages (SP) bit set to zero specifies that the device server shall
perform the specified MODE SELECT
  operation, and shall not save any mode pages. If the logical unit
implements no distinction between current and
  saved mode pages and the SP bit is set to zero, the command shall be
terminated with CHECK CONDITION status,
  . . .
  If my target is not saving mode pages then I am assuming the "logical unit
implements no distinction between current and saved mode pages". If that is
the case then I don't understand the sentence because it would seem the
initiator would have to set SP to 0; but 0 would cause a CHECK CONDITION. So
I think I don't understand the meaning.
  Can someone explain what this means? 

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