VERITAS Volume Manager 3.5 Administrator's Guide (September 2002)

Chapter 3, Administering Dynamic Multipathing (DMP)

Introduction

Example of Multipathing for a Disk Enclosure in a SAN Environment

See “Changing the Disk-Naming Scheme” on page 61 for details of how to change the

naming scheme that VxVM uses for disk devices.

Note The operationof DMPrelieson thevxdmp 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 56 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.

DMP is also informed when you repair or restore a connection, and when you add or

remove devices after the system has been fully booted (provided that the operating

system recognizes the devices correctly).

Host

Fibre Channel

Hubs/Switches

Disk Enclosure enc0

enc0_0

DMP

VxVM

Mapped by DMP

c1t99d0 c2t99d0

c2c1

Disk is c1t99d0 or c2t99d0

depending on the path