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

The appropriate command must be issued to the
array to make the LUNs fail over to the secondary
path.
This policy supports concurrent I/O and load
balancing by having multiple primary paths into
a controller. This functionality is provided by a
controller with multiple ports, or by the insertion
of a SAN switch between an array and a controller.
Failover to the secondary (passive) path occurs
only if all the active primary paths fail.
Active/Passive in explicit failover mode
or non-autotrespass mode (A/P-F)
For Active/Passive arrays with LUN group failover
(A/PG arrays), a group of LUNs that are connected
through a controller is treated as a single failover
entity. Unlike A/P arrays, failover occurs at the
controller level, and not for individual LUNs. The
primary controller and the secondary controller
are each connected to a separate group of LUNs.
If a single LUN in the primary controller’s LUN
group fails, all LUNs in that group fail over to the
secondary controller.
This policy supports concurrent I/O and load
balancing by having multiple primary paths into
a controller. This functionality is provided by a
controller with multiple ports, or by the insertion
of a SAN switch between an array and a controller.
Failover to the secondary (passive) path occurs
only if all the active primary paths fail.
Active/Passive with LUN group failover
(A/P-G)
For this release, only the A/A, A/A-A, and ALUA arrays are supported on HP-UX.
An array policy module (APM) may define array types to DMP in addition to the
standard types for the arrays that it supports.
VxVM uses DMP metanodes (DMP nodes) to access disk devices connected to the
system. For each disk in a supported array, DMP maps one node to the set of paths
that are connected to the disk. Additionally, DMP associates the appropriate
multi-pathing policy for the disk array with the node. For disks in an unsupported
array, DMP maps a separate node to each path that is connected to a disk. The
raw and block devices for the nodes are created in the directories /dev/vx/rdmp
and /dev/vx/dmp respectively.
Figure 4-1 shows how DMP sets up a node for a disk in a supported disk array.
143Administering Dynamic Multi-Pathing
How DMP works