Managing Multipath I/O For Devices; Understanding Multipathing; What Is Multipathing - Novell LINUX ENTERPRISE SERVER 10 - STORAGE ADMINISTRATION GUIDE FOR EVMS Administration Manual

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Table of Contents

Managing Multipath I/O for

Devices

This section discusses how to configure multiple paths between the servers and storage devices for

automatic failover and optional load balancing.

Section 5.1, "Understanding Multipathing," on page 41

Section 5.2, "Before You Begin," on page 44

Section 5.3, "Adding multipathd to the Boot Sequence," on page 46

Section 5.4, "Starting Multipath I/O Services," on page 46

Section 5.5, "Configuring Time-Out Settings for the HBA," on page 46

Section 5.6, "Configuring Multipath I/O for the Root Device," on page 47

Section 5.7, "Scanning for New Devices without Rebooting," on page 47

Section 5.8, "Configuring Multipathing for an Existing Software RAID," on page 48

Section 5.9, "Configuring User-Friendly Names in the /etc/multipath.conf File," on page 49

Section 5.10, "Managing I/O in Error Situations," on page 50

Section 5.11, "Resolving Stalled I/O," on page 50

Section 5.12, "Additional Information," on page 51

Section 5.13, "What's Next," on page 51

5.1 Understanding Multipathing

Section 5.1.1, "What Is Multipathing?," on page 41

Section 5.1.2, "Benefits of Multipathing," on page 42

Section 5.1.3, "Guidelines for Multipathing," on page 42

Section 5.1.4, "Device Mapper," on page 42

Section 5.1.5, "Device Mapper Multipath I/O Module," on page 43

Section 5.1.6, "Multipath Tools," on page 44

5.1.1 What Is Multipathing?

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

device across multiple physical paths between 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 for SCSI connections. Multipathing

provides connection fault tolerance and can optionally provide load balancing across the available

connections.

Multipathing is managed at the device level. It is not possible to manage connections to Linux

partitions contained in the device. You can combine multiple devices to create a software RAID or

volumes as logical devices, but the physical device itself is managed at a lower level.