Chapter 20. SuSE Linux configuration guide
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Draft Document for Review March 28, 2011 12:24 pm
Linux Config.fm
After flushing the paths, use the multipath command with no options to add back mappings for
the devices.
The same command with the -f parameter can be used to remove a single device mapping as
shown in Example 20-16. Run multipath -ll and find the “dm-*” device you want to remove.
Find the scsi id of the device to select the device.
Example 20-16 Remove a single device mapping
# multipath –f 360080e50001b0c90000007504c6e060a
Troubleshooting Guide
Here we present few common problems and ways to troubleshoot:
rescan_scsi_bus.sh is not showing any new device
If the server did not recognize any new mapped LUNs after running the "rescan_scsi_bus.sh"
command a few times, consider rebooting the server.
multipath –ll output does not show all the LUNs.
This most probably is because Device Mapper is not seeing all the LUNs mapped to it. This
can happen due to various reasons,
If mappings are edited with the host connected to the array. The host in some case might fail
to monitor for newly added LUNs and there will not be a scsi block device created for these
newly added LUNs. To fix this issue rescan for the scsi devices using the command
“rescan_scsi_bus”. This should create scsi device for the newly added LUNs and run
“multipath” to add the scsi devices to device mapper table.
multipath does not show paths equal to the number of LUNs mapped
The first thing that you should check is the ‘lsscsi’ output to see if the SCSI midlayer is seeing
(# of paths x # of LUNs) number of block devices.
If not issue a device rescan by “rescan-scsi-bus.sh”. This should fix the issue else reboot the
host.
If “lsscsi” is seeing all the devices, then do the following steps:
Issue “multipath“ so that device mapper can add the devices seen by lsscsi
Flush all the mappings and re-add them (multipath –F ; multipath)
Restart multipath daemon (service multipathd restart)
multipath -ll output is showing the paths as [failed][faulty]
This could happen with the physical path to a controller fails or the controller itself fails and
failover happens.
Verify the disk uid and parameters in multipath.conf file.
Verify cables and zoning configuration.
If this happens after an error in test and you want to make the configuration optimal, save
the logs first, then flush and re-add multipath devices, restart multipath daemon. If the
issue still persists, reboot the system.
Note: It is not possible to flush the mappings while the device is being used by the system.
Unmount any filesystems for /dev/dm-* devices before running this command.
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