Chapter 5. DM-Multipath Administration and Troubleshooting

This chapter will provide information on administering DM-Multipath on a running system. It includes sections on the following topics:

Resizing an Online Multipath Device
The Multipath Daemon
Issues with Large Number of LUNs
Issues with queue_if_no_path feature
Multipath Command Output
Multipath Queries with multipath Command
Multipath Command Options
Multipath Queries with dmsetup Command
Troubleshooting with the multipathd Interactive Console

5.1. Resizing an Online Multipath Device

If you need to resize an online multipath device, use the following procedure.

Resize your physical device.
Use the following command to find the paths to the LUN:
```
# multipath -l
```
Resize your paths. For SCSI devices, writing a 1 to the rescan file for the device causes the SCSI driver to rescan, as in the following command:
```
# echo 1 > /sys/block/device_name/device/rescan 
```
Resize your multipath device by running the multipathd resize command:
```
# multipathd -k'resize map mpath0'
```
Resize the filesystem (assuming no LVM or DOS partitions are used):
```
# resize2fs /dev/mapper/mpath0
```

For further information on resizing an online LUN, see the Online Storage Reconfiguration Guide.

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