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Conference vaxaxp::vmsnotes

Title:VAX and Alpha VMS
Notice:This is a new VMSnotes, please read note 2.1
Moderator:VAXAXP::BERNARDO
Created:Wed Jan 22 1997
Last Modified:Fri Jun 06 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:703
Total number of notes:3722

648.0. "Shadow set remount time too long" by AEOENG::ANTHOINE_J () Mon May 26 1997 11:40

Hi,

	During the tuning of a customer's OpenVMS V7.1 Cluster with 		
	volume-shadowing, we detected the following problem.

	When a local SCSI disk that is a shadow member become inccessible 	
	(because it is physically disconnected), it takes up to 6 minutes to
	be removed from the shadow set.

	In the customer services database, the customer found this is a known
	DKDRIVER problem on OpenVMS V6.2 due to a call to WAIT_UNIT_READY during
	PACKACK attempts. If a disk is not accessible, the routine waits and
	loops 30 times attempting to access the device.


	Is this problem still in OpenVMS V7.1 ?
	The customer's cluster is controlling the futur Subway in PARIS and
	we expect to detect the disk failure in a very short time.
	Is it possible to have quickly an unsupported DKDRIVER with a very 
	short loop ?
	Is it planned to fix this problem in next release ?


	Best regards,
	
	Jacques
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648.1IPMT, PleaseXDELTA::HOFFMANSteve, OpenVMS EngineeringTue May 27 1997 11:334
   Elevate this via IPMT, please -- I'd not want the Paris subway running
   an ECO OpenVMS didn't directly provide nor support...

648.2may not be the problemEVMS::MORONEYvi vi vi - Editor of the BeastTue May 27 1997 18:463
Also check the setting of the SHADOW_MBR_TMO SYSGEN parameter.

-Mike
648.3This is a "known" issueVMSSPT::JENKINSKevin M Jenkins VMS Support EngineeringWed May 28 1997 09:1515
    
    You may go ahead and elevate this, but be prepared. We've been around
    the block on this already... Basically it has been stated that no
    change can be made to DKDRIVERs timeout mechanism. Hence, the best you
    can do is set SHADOW_MBR_TMO real small and that will allow a member
    of a set to be removed in a couple of minutes.... some playing is
    needed to see exactly how small you can set it. 

    On the other hand, we have been investigating a change to the SHDRIVER
    that "might" allow us to "override" the device driver and remove a
    member in a specified time, even if we have not heard back from our
    Pack-Ack. However at this point this sort of change has some
    problems that need to be worked out...

    Kevin
648.4When the new SHDRIVER is available ?AEOENG::ANTHOINE_JFri May 30 1997 04:2410
	The SHADOW_MBR_TMO is set at 5 seconds but it has no influence on
	the behavior of the DKDRIVER. We have tested the system with different
	value from 1 to 60 seconds. The customer would want to detect a disk
	fault ASAP, and more precisely in a maximum of 20 seconds.

	I will be very happy to test the new SHDRIVER. When is it available ?

	Thanks a lot,

	Jacques