Managing Multipath I/O For Devices; Understanding Multipathing; What Is Multipathing; Benefits Of Multipathing - Novell LINUX ENTERPRISE SERVER 11 - STORAGE ADMINISTRATION GUIDE 2-23-2010 Administration Manual

Table of Contents

Managing Multipath I/O for

Devices

This section describes how to manage failover and path load balancing for multiple paths between

the servers and block storage devices.

Section 7.1, "Understanding Multipathing," on page 43

Section 7.2, "Planning for Multipathing," on page 44

Section 7.3, "Multipath Management Tools," on page 50

Section 7.4, "Configuring the System for Multipathing," on page 54

Section 7.5, "Enabling and Starting Multipath I/O Services," on page 60

Section 7.6, "Configuring Path Failover Policies and Priorities," on page 61

Section 7.7, "Tuning the Failover for Specific Host Bus Adapters," on page 69

Section 7.8, "Configuring Multipath I/O for the Root Device," on page 69

Section 7.9, "Configuring Multipath I/O for an Existing Software RAID," on page 70

Section 7.10, "Scanning for New Devices without Rebooting," on page 71

Section 7.11, "Scanning for New Partitioned Devices without Rebooting," on page 73

Section 7.12, "Viewing Multipath I/O Status," on page 74

Section 7.13, "Managing I/O in Error Situations," on page 75

Section 7.14, "Resolving Stalled I/O," on page 76

Section 7.15, "Additional Information," on page 76

Section 7.16, "What's Next," on page 77

7.1 Understanding Multipathing

Section 7.1.1, "What Is Multipathing?," on page 43

Section 7.1.2, "Benefits of Multipathing," on page 43

7.1.1 What Is Multipathing?

Multipathing is the ability of a server to communicate with the same physical or logical block

storage device across multiple physical paths between the host bus adapters in the server and the

storage controllers for the device, typically in Fibre Channel (FC) or iSCSI SAN environments. You

can also achieve multiple connections with direct attached storage when multiple channels are

available.

7.1.2 Benefits of Multipathing

Linux multipathing provides connection fault tolerance and can provide load balancing across the

active connections. When multipathing is configured and running, it automatically isolates and

identifies device connection failures, and reroutes I/O to alternate connections.