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

Foreign devices
DDL may not be able to discover some devices that are controlled by third-party
drivers, such as those that provide multi-pathing or RAM disk capabilities. For
these devices it may be preferable to use the multi-pathing capability that is
provided by the third-party drivers for some arrays rather than using Dynamic
Multi-Pathing (DMP). Such foreign devices can be made available as simple disks
to VxVM by using the vxddladm addforeign command. This also has the effect
of bypassing DMP for handling I/O. The following example shows how to add
entries for block and character devices in the specified directories:
# vxddladm addforeign blockdir=/dev/foo/dsk \
chardir=/dev/foo/rdsk
After adding a current boot disk to the foreign device category, you must reboot
the system. To reboot the system, use the –r option while executing the addforeign
command.
# vxddladm -r addforeign blockpath=/dev/disk/diskname \
charpath=/dev/rdisk/diskname
By default, this command suppresses any entries for matching devices in the
OS-maintained device tree that are found by the autodiscovery mechanism. You
can override this behavior by using the -f and -n options as described on the
vxddladm(1M) manual page.
After adding entries for the foreign devices, use the vxconfigd -kr reset
command to discover the devices as simple disks. These disks then behave in the
same way as autoconfigured disks.
The foreign device feature was introduced in VxVM 4.0 to support non-standard
devices such as RAM disks, some solid state disks, and pseudo-devices such as
EMC PowerPath.
Foreign device support has the following limitations:
■ A foreign device is always considered as a disk with a single path. Unlike an
autodiscovered disk, it does not have a DMP node.
■ It is not supported for shared disk groups in a clustered environment. Only
standalone host systems are supported.
■ It is not supported for Persistent Group Reservation (PGR) operations.
■ It is not under the control of DMP, so enabling of a failed disk cannot be
automatic, and DMP administrative commands are not applicable.
■ Enclosure information is not available to VxVM. This can reduce the availability
of any disk groups that are created using such devices.
97Administering disks
Discovering and configuring newly added disk devices