HP StorageWorks Device Mapper Multipath Enablement Kit for HP StorageWorks Disk Arrays installation and reference guide (AA-RW8RE-TE, June 2009)

6 Troubleshooting
Following are the troubleshooting steps for issues that you may encounter while using DM Multipath:
• Enter the following commands whenever a new LUN is added or deleted at the Linux host, to update
the multipath maps in the kernel:
1. /etc/init.d/multipathd restart
2. multipath -v <X>
• If SELinux is enabled, device maps cannot be created and SELinux denies access requested by /
sbin/multipathd.
NOTE:
In some cases, labelling problems can cause SELinux denials. Try to restore the default system file
context for bin by running the following commends:
restorecon -v bin
If this does not work, there is currently no automatic way to allow this access. Instead, you can
generate a local policy module to allow this access - For more information, see the following
website: http://fedora.redhat.com/docs/selinux-faq-fc5/#id2961385
You can also disable SELinux protection altogether. However, disabling SELinux protection is not
recommended.
• If an existing LUN is deleted and a new LUN is presented in the same SCSI slot, LUN collision
may occur. This results in the creation of a new LUN through old device special files. This may
lead to data corruption. To recover from this error state, run the following commands:
1. multipath -F
2. hp_rescan -a or echo "- - -" > /sys/class/scsi_host/<host instance>/
scan
3. /etc/init.d/multipathd restart
4. /sbin/multipath -v3
• Path status may not be reflected immediately when it is recovered from FAILED to ACTIVE state.
To reflect the correct path state run the following commands.
1. /etc/init.d/multipathd restart
2. /sbin/multipath -v3
• On hosts running SLES OS, if you do not enable boot.multipath to start at boot time, multipath
maps are not created. To ensure the creation of device maps across reboots, enable boot.mul-
tipath using the following command:
# chkconfig boot.multipath on
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