Download HP 3PAR Red Hat Enterprise Linux and Oracle Linux

NOTE: If you see the device status as [undef] in the output, this is an RHEL defect that has
been raised with RHEL to be fixed. Instead, use the multipath -ll command, which shows the
correct device status as ready.
The dmsetup command can be used with various options to get more information on Device-mapper
mappings.
Example:
# dmsetup table
350002ac001b40031: 0 10485760 multipath 1 queue_if_no_path 0 1 1 round-robin 0 2 1
8:0 100 8:16 100
# dmsetup ls --target multipath
350002ac0004b0079
(253, 7)
# dmsetup info 350002ac0004b0079
Name:
350002ac0004b0079
State:
ACTIVE
Read Ahead:
256
Tables present:
LIVE
Open count:
1
Event number:
0
Major, minor:
253, 7
Number of targets: 1
UUID: mpath-350002ac0004b0079
# dmsetup table --target multipath
350002ac0004b0079: 0 10485760 multipath 1 queue_if_no_path 0 1 1 round-robin 0 2 1
8:32 100 8:48 100
Partitioning Device-mapper Nodes
The following section provides guidelines for partitioning Device-mapper nodes.
When partitioning a Device-mapper node, do not use fdisk on the /dev/mapper/XXX nodes.
The following error output may be seen as a result of using fdisk.
WARNING! Rereading the partition table failed with error 22: Invalid argument. The kernel still
uses the old table. The new table will be used at the next reboot. Syncing disks
NOTE:
Do not use the fdisk command with /dev/mapper/XXX devices to create partitions.
Use fdisk on the underlying disks /dev/sdXX and execute the following command when
Device-mapper multipath maps the device to create a /dev/mapper/<device node> partition.
# multipath -l
50002ac001b40031
[size=5 GB][features="1 queue_if_no_path"][hwhandler="0"]
\_ round-robin 0 [active]
\_ 0:0:0:0 sda 8:0 [active]
\_ 1:0:0:0 sdb 8:16 [active]
Device-mapper node 350002ac001b40031 is formed from underlying devices sda and sdb
representing two paths from the same storage volume.
# fdisk /dev/sda -- create a partition
118
Modifying HP 3PAR Devices on the Host