Veritas Volume Manager 5.1 SP1 Administrator"s Guide (5900-1506, April 2011)

See the vxdg(1M) manual page.
See “Handling of minor number conflicts” on page 224.
Compatibility of disk groups between platforms
For disk groups that support the Cross-platform Data Sharing (CDS) feature, the
upper limit on the minor number range is restricted on AIX, HP-UX, Linux (with
a 2.6 or later kernel) and Solaris to 65,535 to ensure portability between these
operating systems.
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:
231Creating and administering disk groups
Moving disk groups between systems