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

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 and 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.
Active/Passive with LUN group failover
(A/P-G)
Variants of the A/P, AP/F and A/PG array types
that support 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 hub or switch between an array and a
controller. Failover to the secondary (passive)
path occurs only if all the active primary paths
fail.
Concurrent Active/Passive (A/P-C)
Concurrent Active/Passive in explicit
failover mode or non-autotrespass
mode (A/PF-C)
Concurrent Active/Passive with LUN
group failover (A/PG-C)
An array support library (ASL) 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
multipathing 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 3-1 shows how DMP sets up a node for a disk in a supported disk array.
139Administering Dynamic Multipathing
How DMP works