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Handling disks with duplicated identifiers

Advanced disk arrays provide hardware tools that you can use to create clones of existing disks outside the control of VxVM. For example, these disks may have been created as hardware snapshots or mirrors of existing disks in a disk group.As a result, the VxVM private region is also duplicated on the cloned disk. When the disk group containing the original disk is subsequently imported, VxVM detects multiple disks that have the same disk identifier that is defined in the private region. In releases prior to 5.0, if VxVM could not determine which disk was the original, it would not import such disks into the disk group. The duplicated disks would have to be re-initialized before they could be imported.

From release 5.0, a unique disk identifier (UDID) is added to the disk's private region when the disk is initialized or when the disk is imported into a disk group (if this identifier does not already exist). Whenever a disk is brought online, the current UDID value that is known to the Device Discovery Layer (DDL) is compared with the UDID that is set in the disk's private region. If the UDID values do not match, the udid_mismatch flag is set on the disk. This flag can be viewed with the vxdisk list command.

A new set of vxdisk and vxdg operations are provided to handle such disks; either by either writing the DDL value of the UDID to a disk's private region, or by tagging a disk and specifying that it is a cloned disk to the vxdg import operation.

The following is sample output from the vxdisk list command showing that disks sdg, sdh and sdi are marked with the udid_mismatch flag:

# vxdisk list


sda auto:cdsdisk - - online

sdb auto:cdsdisk - - online


sde auto:cdsdisk - - online

sdf auto:cdsdisk - - online

sdg auto:cdsdisk - - online udid_mismatch

sdh auto:cdsdisk - - online udid_mismatch

sdi auto:cdsdisk - - online udid_mismatch