Technical data

6 Troubl eshooting

Following are the troubleshooting steps for issues that you may encou nter while using HPDM 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:

/etc/init.d/multipathd restart

multipath -v <X>

• Enter the following commands whenever multipath devices are deleted using multipath -F,to

create the multipath devices and to create the same for the partitions on the multipath devices:

multipath -v <X>

/sbin/dmsetup ls --target multipath --exec "/sbin/kpartx -a –p

–part" (SLES10/ SLES10 SP1)

/sbin/dmsetup ls --target multipath --exec "/sbin/kpartx –a" (RHEL

4U5/RHEL 4U6/RHEL 5/RHEL 5U1)

• 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:h

ttp://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, LU N 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 following comm ands:

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 recoved 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.multipath using the following command:

# chkconfig boot.multipath on

Device Mapper Multipath Enablement Kit for HP StorageWorks Disk Arrays