Dell PowerVault MD3200 Owner's Manual - Page 175
Troubleshooting
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Troubleshooting Question Answer How can I check if multipathd Run the following command is running? /etc/init.d/multipathd status Why does the multipath -ll command output not show any devices? 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. Why is a newly-mapped LUN not assigned a multipathing device node? Run "rescan_dm_devs" in any directory. This should bring up the devices. I have no LUNs mapped before. Run rescan_dm_devs instead of rescanThen I map a few LUNs. After scsi-bus for LUN 0 reconfiguration. running rescan-scsibus.sh, LUN 0 does not show up. 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 to remove the multipathing mapping. For example, if device devices related with /dev/dm-1 is deleted, you must run multipath -f /dev/dm-1 to remove /dev/dm-1 from DM mapping table. If multipathing daemon is stopped/restarted, run multipath -F to 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 175