VERITAS Volume Manager 3.1 Administrator's Guide

Disk Group Tasks
Reserving Minor Numbers for Disk Groups
Chapter 5230
Reserving Minor Numbers for Disk Groups
Disk groups can be moved between systems. When you allocate volume
device numbers in separate ranges for each disk group, all disk groups in
a group of machines can be moved without causing device number
collisions.
Volume Manager allows you to select a range of minor numbers for a
specified disk group. You use this range of numbers during the creation
of a volume. This guarantees that each volume has the same minor
number across reboots or reconfigurations. If two disk groups have
overlapping ranges, an import collision is detected and an avoidance or
renumbering mechanism is then needed.
To set a base volume device minor number for a disk group, use the
following command:
# vxdg init diskgroup minor= base_minor devicename
Volume device numbers for a disk group are chosen to have minor
numbers starting at this base_minor number. Minor numbers (on most
systems) can range up to 131071. A reasonably sized range can be left at
the end for temporary device number remappings (in the event that two
device numbers still conflict).
If you do not specify a minor operand on the vxdg init command line,
the Volume Manager chooses a random number. The number chosen is at
least 1000 or is a multiple of 1000, and yields a usable range of 1000
device numbers. The chosen default number does not overlap within a
range of 1000 of any currently imported disk groups. It also does not
overlap 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 usingfail-over mechanisms,you should
select ranges that avoid overlap.
For further information on minor number reservation, see the vxdg(1M)
manual page.