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Configuration: Device Mapper Multipath for Linux 217
Important Information About Special Partitions
When using Device Mapper with the MD3600f Series array, all physical disks
are assigned a disk device node. This includes a special device type used for
in-band management of the MD3600f Series array, known as the Access Disk
or Universal Xport device.
CAUTION: Certain commands, such as lsscsi, displays one or more instances of
Universal Xport devices. These device nodes must never be accessed, mounted, or
used in any way. Doing so could cause loss of communication to the storage array
and possibly cause serious damage to the storage array, potential making data
stored on the array inaccessible.
Only multipathing device nodes and partition nodes created using the
directions provided above should be mounted or in any way accessed by the
host system or its users.
Table 14-1. Device Mapper Commands
Command Descriptions
multipath -h Prints usage information.
multipath -ll Displays the current multipath topology using all
available information (sysfs, the device mapper,
path checkers, and so on).
multipath Re-aggregates multipathing device with
simplified output.
multipath -f
<multipath_dev_node>
Flushes out Device Mapper for the specified
multipathing device. Used if the underlying
physical devices are deleted/unmapped.
multipath -F Flushes out all unused multipathing device maps.
rescan_dm_devs Dell provided script. Forces a rescan of the host's
SCSI bus and aggregates multipathing devices as
needed. For use when:
• LUNs are dynamically mapped to the hosts.
• New targets are added to the host.
• Failback of the storage array is required.
book.book Page 217 Wednesday, June 8, 2011 5:01 PM