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Status Not under consideration
Workspace AIX
Created by Guest
Created on Aug 28, 2018

Make chdev aware of third party volume managers using disk devices.

Recently we've had a major incident in one of our biggest customers involving Oracle ASM disks that are virtualized using dual VIOS and vscsi. In one of the VIOS, PVIDs were assigned on disks already in use by Oracle ASM running in a client LPAR. This did overwrite ASM administrative information becoming these disks unusable by ASM. This PVID assignation also affected client Lpars running RedHat. On these virtual machines the information regarding the disk partitioning was overwritten.
The situation was fixed running some oracle procedures to recreate the administative information and reinstalling the RedHat virtual Machines.
Investigating the behaviour of some lvm commands we found that If and administrator issues the command mkvg using a disk that has been assigned to ASM mkvg figures out that that disk is in use by a third party volume manager and it fails explaining the issue.
On the other hand a command like "chdev -a pv=yes" would record the PVID, overwritting any administrative info existing on the disk and making it unusable for some other volume manager that was using that disk.
If a disk is in use by a third party volume manager it would be an interesting enhancement that chdev command (or other command that issues similar functions) would present a warning pointing that you are about to change a disk probably belonging to a third party volume manager or asking for confirmation or request some "force" flag to procede.

Idea priority High
  • Guest
    Sep 17, 2018

    The lkdev command has been provided to address the issue described in this RFE. This approach is preferable to attempting to update the AIX disk configuration code to recognize every possible 3rd party volume manager that could have written data to the disk.

    AIX lkdev Command:

    The AIX lkdev command should be used by the system administrator when a disk is assigned to Oracle to lock the disk device to prevent the device from inadvertently being altered by a system administrator at a later time. The lkdev command locks the specified device so that any attempt to modify the device attributes (chdev, chpath) or remove the device or one of its paths (rmdev, rmpath) will be denied. This is intended to get the attention of the administrator and warn that the device is already being used. The ???-d" option of the lkdev command can be used to remove the lock if the disk is no long being used by Oracle. The lspv command with the ???-u" option indicates if the disk device is locked. The example section of this note shows how to use lkdev and the related lspv output.

  • Guest
    Sep 4, 2018

    We added a command lkdev for third party volume management, which locks a device and any attempt to modify device characteristics fails. There are articles published in google.