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189Creating and administering disk groups
Moving disk groups between systems
reminor
operation on the nodes that are in the cluster to resolve the conflict. In
a cluster where more than one node is joined, use a base minor number which
does not conflict on any node.
For further information on minor number reservation, see the vxdg(1M)
manual page.
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 runs 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.