VERITAS Volume Manager 4.1 Administrator's Guide

Administering Dynamic Multipathing (DMP)
How DMP Works
Chapter 3112
the disk array with the node. For disks in an unsupported array, DMP maps a separate
metanode 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.
See the figure “How DMP Represents Multiple Physical Paths to a Disk as one Metanode,” for
an illustration of how DMP sets up a metanode for a disk in a supported disk array.
Figure 3-1 How DMP Represents Multiple Physical Paths to a Disk as one
Metanode
As described in “Enclosure-Based Naming” on page 7, VxVM implements a disk device
naming scheme that allows you to recognize to which array a disk belongs. The figure,
“Example of Multipathing for a Disk Enclosure in a SAN Environment,”, shows that two
paths, c1t99d0 and c2t99d0, exist to a single disk in the enclosure, but VxVM uses the single
DMP metanode, enc0_0, to access it.
Single DMP
Metanode
Multiple
Paths
DMP
VxVM
Mapped by DMP
Multiple
Paths
Host
Disk
c2c1