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Restoring CDS disk labels

CDS disks have the following labels:

• Platform block
• AIX coexistence label
• HP-UX coexistence or VxVM ID block

There are also backup copies of each. If any of the primary labels become corrupted, VxVM will not bring the disk online and user intervention is required.

If two labels are intact, the disk is still recognized as a cdsdisk (though in the error state) and vxdisk flush can be used to restore the CDS disk labels from their backup copies.

Primary labels are at sectors 0, 7, and 16; and a normal flush will not flush sectors 7 and 16. Also, the private area is not updated as the disk is not in a disk group. There is no means of finding a "good" private region to flush from. In this case, it is possible to restore the CDS disk labels from the existing backups on disk using the flush operation.

If a corruption happened after the labels were read and the disk is still online and part of a disk group, then a flush operation will also flush the private region.

 To rewrite the CDS ID information on a specific disk

• Type the following command:

  # vxdisk flush disk_access_name

This rewrites all labels except sectors 7 and 16

 To rewrite all the disks in a CDS disk group

• Type the following command:

  # vxdg flush diskgroup

This rewrites all labels except sectors 7 and 16

 To forcibly rewrite the AIX coexistence label in sector 7 and the HP-UX coexistence label or VxVM ID block in sector 16

• Type the following command:

  # vxdisk -f flush disk_access_name

This command rewrites all labels if there exists a valid VxVM ID block that points to a valid private region. The -f option is required to rewrite sectors 7 and 16 when a disk is taken offline due to label corruption (possibly by a Windows system on the same fabric).