HP 3PAR Ubuntu Operating System Implementation Guide

State: ACTIVE
Read Ahead: 256
Tables present: LIVE
Open count: 0
Event number: 1
Major, minor: 253, 0
Number of targets: 1
UUID: mpath-350002ac001dc0031
# dmsetup table --target multipath
350002ac001dc0031: 0 4194304 multipath 1 queue_if_no_path 0 1 1 round-robin 0 2 1 8:0
1000 8:16 1000
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
After the fdisk command completes, use the kpartx command to list and create DM devices
for the partitions on the device.
# kpartx /dev/mapper/350002ac001b40031
350002ac001b40031 -part1 : 0 10477194 /dev/mapper/350002ac001b40031 62
# kpartx -a /dev/mapper/350002ac001b40031 -- will add a partition mapping
# ls /dev/mapper
350002ac001b40031 350002ac001b40031 -part1
30 Modifying HP 3PAR Devices on the Host Server