HP VMA SAN, Руководство по установке и настройке

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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