HP VMA-series Memory Arrays Podręcznik Użytkownika Pobierz pdf (Strona 63)

AM456-9025A HP VMA SAN Gateway Installation and Configuration Guide 63

CHAPTER 6 Multipath Client-Side Configuration

This chapter provides examples of client-side multipath setup for the HP VMA

SAN Gateway. The following topics are covered:

• Multipath Overview on page 60

• Multipath Setup on page 61

Note: The examples in this chapter are guidelines for (client-side) Red Hat

Enterprise Linux 5.x DM Multipath. For more information, go to the Red Hat Web

site: http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/

Multipath Overview

Multipath I/O is commonly used when there is more than one physical path

between the system CPU and the storage devices. The redundant paths are

leveraged to increase performance and fault-tolerance.

Device Mapper Multipath (DM Multipath, Red Hat Enterprise Linux) is the

multipathing utility used in the example presented in this chapter. DM Multipath is

a generic framework that maps each physical path to a SCSI device represented as

a separate

/dev entry in a form of a block device. DM Multipath provides means

of combining multiple such block devices into a single block device. DM Multipath

uses Device Mapper kernel framework for mapping IOs between individual paths

and user-space daemon

multipathd for providing configuration and policy for

the mapped device.

To determine which devices (and paths) correspond to a particular LUN, DM

Multipath initiates a query. The response to the query returns the LUN serial

number (among other information). The serial number for a LUN remains the

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HP VMA-series Memory Arrays Podręcznik Użytkownika Strona 63