VERITAS Volume Manager 3.5 Administrator's Guide (September 2004)

Administering Dynamic Multipathing (DMP)
Introduction
Chapter 3108
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.
Figure 3-2 Example of Multipathing for a Disk Enclosure in a SAN
Environment
See “Changing the Disk-Naming Scheme” on page 76 for details of how
to change the naming scheme that VxVM uses for disk devices.
NOTE The operation of DMP relies on the vxdmp device driver. Unlike prior
releases, from VxVM 3.1.1 onwards, the vxdmp driver must always be
present on the system.
See “Configuring Newly Added Disk Devices” on page 70 for a
description of how to make newly added disk hardware known to a host
system.
Path Failover Mechanism
The DMP feature of VxVM enhances system reliability when used with
multiported disk arrays. In the event of the loss of one connection to the
disk array, DMP automatically selects the next available I/O path for I/O
requests dynamically without action from the administrator.
Host
Fibre Channel
Hubs/Switches
Disk Enclosure enc0
enc0_0
DMP
VxVM
Mapped by DMP
c1t99d0 c2t99d0
c2c1
Disk is c1t99d0 or
c2t99d0