Error Message

 

TagmaStore-USP0_0 auto:aixdisk    -            (datadg)  online   aliasedTagmaStore-USP0_8 auto:aixdisk    -            (datadg)  online   aliased

 

To identify what caused the state of the disk to change to set the "aliased" flag, we need to identify what has caused the discrepancy in the disk format. The most likely reasons could be:

• If we do not remove the foreign devices correctly prior to upgrade from versions prior to VxVM 4.1 to VxVM version 4.1/5.0/5.1 as per recommend procedures in the Storage Foundation Installation Guide
• If the disk has been re-initialized as a different format, for example, if the disk was originally a "cdsdisk" format and has been mistakenly re-initialized as a "simple" disk format
• If the disk has been mistakenly presented to other systems simultaneously and used when they are currently being used in existing VxVM configurations
• Any other user action or structural change to the header of the disk which may cause such discrepancy of the disk format between the vxconfigd in-core DA record and private region header stored on the physical disk.

To recover from the situation, the only possible way is to re-initialize the disk with the original offsets and lengths of the Volume Manager Private and Public regions and ensuring to define the same format of the disk as that of the original configuration.

If all the disks in the diskgroup are in the same "online aliased" state, then it is important to have a valid configuration backup to be able to re-initialize the disks correctly and re-build the diskgroup shell.

The minimum requirements to ensure that the disks can be re-initialized correctly and the diskgroup shell be re-constructed to match that of the original configuration are:

• A valid "vxdisk list " output for each disk in the "online aliased" state collected prior to the disk getting into this state. The device names should not have changed at the OS level, otherwise we may need the exact OS device mappings too with the VxDMP dmpnode names. (The best possible way to confirm this is via the Serial Numbers of the devices as with the previous mappings with the VxDMP dmpnode names).
• A valid vxprint output of the diskgroup or the output of the "vxprivutil dumpconfig" from the private region of the disks in the diskgroup prior to the disk(s) getting into the "online aliased" state.

There are various flags that vxconfigd can set on disks in Volume Manager depending on the state of the device. One such state of a disk in Volume Manager is that of "online aliased", which is identified in the "vxdisk list" output. We see the ‘aliased’ flag associated with a disk in Volume Manager only when there is a mismatch of the disk format between the vxconfigd in-core DA record and private region header which is stored on the physical disk. This will cause the disks to be unusuable in Volume Manager and the diskgroup will not be able to import. However, the diskgroup may be forcefully imported if there are other valid disks with configuration information on those disks that are not set with the 'aliased' flag. This means that the data on those volumes may not be accessible because the volumes cannot be started which are having the devices with the 'aliased' flag set.