Enabling And Starting Multipath I/O Services; Configuring Path Failover Policies And Priorities; Configuring The Path Failover Policies - Novell LINUX ENTERPRISE SERVER 10 SP2 - STORAGE ADMINISTRATION GUIDE 05-15-2009 Administration Manual

5.5 Enabling and Starting Multipath I/O Services

To start multipath services and enable them to start at reboot:
1 Open a terminal console, then log in as the
2 At the terminal console prompt, enter
chkconfig multipathd on
chkconfig boot.multipath on
If the boot.multipath service does not start automatically on system boot, do the following:
1 Open a terminal console, then log in as the
2 Enter
/etc/init.d/boot.multipath start
/etc/init.d/multipathd start
5.6 Configuring Path Failover Policies and
Priorities
In a Linux host, when there are multiple paths to a storage controller, each path appears as a separate
block device, and results in multiple block devices for single LUN. The Device Mapper Multipath
service detects multiple paths with the same LUN ID, and creates a new multipath device with that
ID. For example, a host with two HBAs attached to a storage controller with two ports via a single
unzoned Fibre Channel switch sees four block devices:
. The Device Mapper Multipath service creates a single block device,
dev/sdd
that reroutes I/O through those four underlying block devices.
mpath1
This section describes how to specify policies for failover and configure priorities for the paths.
Section 5.6.1, "Configuring the Path Failover Policies," on page 59
Section 5.6.2, "Configuring Failover Priorities," on page 60
Section 5.6.3, "Using a Script to Set Path Priorities," on page 65
Section 5.6.4, "Configuring ALUA," on page 65
Section 5.6.5, "Reporting Target Path Groups," on page 67

5.6.1 Configuring the Path Failover Policies

Use the command with the -p option to set the path failover policy:
multipath
multipath devicename -p policy
Replace policy with one of the following policy options:
Group Policy Options for the multipath -p Command
Table 5-4
Policy Option Description
failover One path per priority group.
user or equivalent.
root
user or equivalent.
root
,
/dev/sda /dev/sdb
Managing Multipath I/O for Devices
, , and
/dev/sdc /
/dev/mpath/
59