Troubleshooting

QuestionAnswer

How can I check if multipathd is running?

Why does the multipath –llcommand output not show any devices?

Why is a newly-mapped LUN not assigned a multipathing device node?

Run the following command

/etc/init.d/multipathd status

First verify if the devices are discovered or not. The command #cat /proc/scsi/scsi displays all the devices that are already discovered.

Then verify the multipath.conf to ensure that it is been updated with proper settings.

After this, run multipath. Then run multipath –ll, the new devices should be displayed.

Run “rescan_dm_devs” in any directory. This should bring up the devices.

I have no LUNs mapped before. Then I map a few LUNs. After running rescan-scsi- bus.sh, LUN 0 does not show up.

Run rescan_dm_devs instead of rescan- scsi-bus for LUN 0 reconfiguration.

I removed a LUN, but the multipathing mapping is still present.

The multipathing device is still there after you remove the LUNs. Run multipath –f<device node for the deleted LUN> to remove the multipathing mapping. For example, if device devices related with /dev/dm-1 is deleted, you must run multipath –f /dev/dm-1to remove /dev/dm-1 from DM mapping table. If multipathing daemon is stopped/restarted, run multipath –Fto flush out all stale mappings.

Failback does not happen as expected with the array.

Sometimes the low level driver cannot auto-detect devices coming back with the array. Run rescan_dm_devs to do a rescan of the host server SCSI bus and re-aggregate devices at multipathing layer.

Configuration: Device Mapper Multipath for Linux

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Dell MD3620F, MD3600f owner manual Troubleshooting, 219, QuestionAnswer
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