VERITAS Volume Manager 3.5 Administrator's Guide (September 2002)

Moving Disk Groups Between Systems
120 VERITAS Volume Manager Administrator’s Guide
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 movea disk group between systems,it is possiblefor the minornumbers that it
used on its previous system to coincide (or collide) with those of objects known to VxVM
on thenew system. To getaround this potential problem, you can allocate separateranges
of minor numbers for each disk group. VxVM uses the specified range of minor numbers
when it creates volume objects from the disks inthe 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.
To set a base volume device minor number for a disk group, use the following command:
# vxdg init diskgroup minor=base_minor devicename
VxVM chooses minor device numbers for objects created from this disk group starting at
the number base_minor. Minor numbers can range from 0 up to 16,777,215. Try to leave a
reasonable number of unallocated minor numbers near the top of this range to allow for
temporary device number remapping in the event that a device minor number collision
may still occur.
If you do not specify the base of the minornumber range for a disk group, VxVM chooses
one at random. The number chosen is at least 1000, is a multiple of 1000, and yields a
usable range of 1000 device numbers. The chosen number also does not overlap within a
rangeof 1000ofany currently imported diskgroups,andit does notoverlap any currently
allocated volume device numbers.
Note The default policy ensures that a small number of disk groups can be merged
successfully between a set of machines. However, where disk groups are merged
automatically using failover mechanisms, select ranges that avoid overlap.
For further information on minor number reservation, see the vxdg(1M) manual page.