Veritas Volume Manager 5.0.1 Administrator's Guide, HP-UX 11i v3, First Edition, November 2009

On a Linux platform with a pre-2.6 kernel, the number of minor numbers per
major number is limited to 256 with a base of 0. This has the effect of limiting the
number of volumes and disks that can be supported system-wide to a smaller
value than is allowed on other operating system platforms. The number of disks
that are supported by a pre-2.6 Linux kernel is typically limited to a few hundred.
With the extended major numbering scheme that was implemented in VxVM 4.0
on Linux, a maximum of 4079 volumes could be configured, provided that a
contiguous block of 15 extended major numbers was available.
VxVM 4.1 and later releases run on a 2.6 version Linux kernel, which increases
the number of minor devices that are configurable from 256 to 65,536 per major
device number. This allows a large number of volumes and disk devices to be
configured on a system. The theoretical limit on the number of DMP and volume
devices that can be configured on such a system are 65,536 and 1,048,576
respectively. However, in practice, the number of VxVM devices that can be
configured in a single disk group is limited by the size of the private region.
When a CDS-compatible disk group is imported on a Linux system with a pre-2.6
kernel, VxVM attempts to reassign the minor numbers of the volumes, and fails
if this is not possible.
To help ensure that a CDS-compatible disk group is portable between operating
systems, including Linux with a pre-2.6 kernel, use the following command to set
the maxdev attribute on the disk group:
# vxdg -g diskgroup set maxdev=4079
Note: Such a disk group may still not be importable by VxVM 4.0 on Linux with a
pre-2.6 kernel if it would increase the number of minor numbers on the system
that are assigned to volumes to more than 4079, or if the number of available
extended major numbers is smaller than 15.
You can use the following command to discover the maximum number of volumes
that are supported by VxVM on a Linux host:
# cat /proc/sys/vxvm/vxio/vol_max_volumes
4079
See the vxdg(1M) manual page.
Handling conflicting configuration copies
If an incomplete disk group is imported on several different systems, this can
create inconsistencies in the disk group configuration copies that you may need
221Creating and administering disk groups
Handling conflicting configuration copies