Creating and administering disk groups 187

Moving disk groups between systems

The following error message indicates a recoverable error.

VxVM vxdg ERROR V-5-1-587 Disk group groupname: import failed:

Disk for disk group not found

If some of the disks in the disk group have failed, you can force the disk group to be imported by specifying the -foption to the vxdg import command:

#vxdg -f import diskgroup

Caution: Be careful when using the -foption. It can cause the same disk group to be imported twice from different sets of disks. This can cause the disk group configuration to become inconsistent.

See “Handling conflicting configuration copies” on page 190.

As using the -foption to force the import of an incomplete disk group counts as a successful import, an incomplete disk group may be imported subsequently without this option being specified. This may not be what you expect.

These operations can also be performed using the vxdiskadm utility. To deport a disk group using vxdiskadm, select menu item 8 (Remove access to (deport) a disk group). To import a disk group, select item 7 (Enable access to (import) a disk group). The vxdiskadm import operation checks for host import locks and prompts to see if you want to clear any that are found. It also starts volumes in the disk group.

Reserving minor numbers for disk groups

A device minor number uniquely identifies some characteristic of a device to the device driver that controls that device. It is often used to identify some characteristic mode of an individual device, or to identify separate devices that are all under the control of a single controller. VxVM assigns unique device minor numbers to each object (volume, plex, subdisk, disk, or disk group) that it controls.

When you move a disk group between systems, it is possible for the minor numbers that it used on its previous system to coincide (or collide) with those of objects known to VxVM on the new system. To get around this potential problem, you can allocate separate ranges of minor numbers for each disk group. VxVM uses the specified range of minor numbers when it creates volume objects from the disks in the disk group. This guarantees that each volume has the same minor number across reboots or reconfigurations. Disk groups may then be moved between machines without causing device number collisions.

VxVM chooses minor device numbers for objects created from this disk group starting at the base minor number base_minor. Minor numbers can range from this value up to 16,777,215. Try to leave a reasonable number of unallocated