HP 3PAR SUSE Linux Enterprise Implementation Guide

NOTE: With no_path_retry set to a value other than 0 in the /etc/multipath.conf file,
I/O will be queued for the period of the retries and features=1 queue_if_no_path will be
shown in multipath -l command output.
Example:
#multipath -l
350002ac001dc0031 dm-0 3PARdata,VV
[size=2.0G][features=1 queue_if_no_path][hwhandler=0][rw]
\_ round-robin 0 [prio=-2][active]
\_ 2:0:0:99 sda 8:0 [active][undef]
\_ 3:0:0:99 sdb 8:16 [active][undef
NOTE: If you see the device status as [undef] in the output, this is a SUSE defect. Instead, use
multipath -ll command, which shows the correct device status as ready.
Example:
# multipath -ll
350002ac001dc0031 dm-0 3PARdata,VV
[size=2.0G][features=1 queue_if_no_path][hwhandler=0][rw]
\_ round-robin 0 [prio=2][active]
\_ 2:0:0:99 sda 8:0 [active][ready]
\_ 3:0:0:99 sdb 8:16 [active][ready]
The dmsetup command can be used with various options to get more information on Device-mapper
mappings.
Example:
# dmsetup table
350002ac001dc0031: 0 4194304 multipath 1 queue_if_no_path 0 1 1 round-robin 0 2 1 8:0 1000 8:16 1000
# dmsetup ls --target multipath
350002ac001dc0031 (253, 0)
# dmsetup info 350002ac0004b0079
350002ac001dc0031 (253, 0)
# dmsetup info 350002ac001dc0031
Name: 350002ac001dc0031
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.
Partitioning Device-mapper Nodes 59