Multi-Path I/O (MPIO) helps provide increased availability
of virtual Small Computer Serial Interface (SCSI) resources by providing
redundant paths to the resource. This topic describes how to set up
Multi-Path I/O for AIX® client
logical partitions.
In order to provide MPIO to
AIX client logical partitions,
you must have two
Virtual I/O Server logical
partitions configured on your system. This procedure assumes that
the disks are already allocated to both the
Virtual I/O Server logical partitions
involved in this configuration.
Note: You can also configure MPIO on Linux logical partitions.
For more information, see the documentation for the Linux operating system.
To configure MPIO, follow these steps. In this scenario,
hdisk5 in the first
Virtual I/O Server logical
partition, and hdisk7 in the second
Virtual I/O Server logical partition,
are used in the configuration.
The following figure shows the configuration
that will be completed during this scenario.
Using the preceding figure as a guide, follow these steps:
- Using the HMC,
create SCSI server adapters on the two Virtual I/O Server logical partitions.
- Using the HMC,
create two virtual client SCSI adapters on the client logical partitions,
each mapping to one of the Virtual I/O Server logical partitions.
- On either of the Virtual I/O Server logical partitions,
determine which disks are available by typing lsdev -type
disk. Your results look similar to the following:
name status description
hdisk3 Available MPIO Other FC SCSI Disk Drive
hdisk4 Available MPIO Other FC SCSI Disk Drive
hdisk5 Available MPIO Other FC SCSI Disk Drive
Select which disk that you want to use in the MPIO configuration.
In this scenario, hdisk5 is selected.
- Determine the ID of the disk that you have selected. For
instructions, see Identifying exportable disks.
In this scenario, the disk does not have an IEEE volume attribute
identifier or a unique identifier (UDID). Hence, determine the physical
identifier (PVID) by running the lspv hdisk5 command.
Your results look similar to the following:
hdisk5 00c3e35ca560f919 None
The
second value is the PVID. In this scenario, the PVID is 00c3e35ca560f919.
Note this value.
- List the attributes of the disk on the first Virtual I/O Server by using the lsdev command.
In this scenario, type lsdev -dev hdisk5 -attr. Your
results look similar to the following
..
lun_id 0x5463000000000000 Logical Unit Number ID False
..
..
pvid 00c3e35ca560f9190000000000000000 Physical volume identifier False
..
reserve_policy single_path Reserve Policy True
Note the values for lun_id and reserve_policy. If the
reserve_policy attribute is set to anything other than no_reserve,
then you must change it. Set the reserve_policy to no_reserve by
typing chdev -dev hdiskx -attr reserve_policy=no_reserve.
- On the second Virtual I/O Server logical partition,
list the physical volumes by typing lspv. In the
output, locate the disk that has the same PVID as the disk identified
previously. In this scenario, the PVID for hdisk7 matched:
hdisk7 00c3e35ca560f919 None
Tip: Although the PVID values should be identical, the disk
numbers on the two Virtual I/O Server logical
partitions might vary.
- Determine if the reserve_policy attribute is set to no_reserve
using the lsdev command. In this scenario, type lsdev
-dev hdisk7 -attr. You see results similar to the following:
..
lun_id 0x5463000000000000 Logical Unit Number ID False
..
pvid 00c3e35ca560f9190000000000000000 Physical volume identifier False
..
reserve_policy single_path Reserve Policy
If
the reserve_policy attribute is set to anything other than no_reserve,
you must change it. Set the reserve_policy to no_reserve by
typing chdev -dev hdiskx -attr reserve_policy=no_reserve.
- On both Virtual I/O Server logical
partitions, use the mkvdev to create the virtual devices. In
each case, use the appropriate hdisk value. In this scenario, type
the following commands:
- On the first Virtual I/O Server logical
partition, type mkvdev -vdev hdisk5 -vadapter vhost5 -dev
vhdisk5
- On the second Virtual I/O Server logical
partition, type mkvdev -vdev hdisk7 -vadapter vhost7 -dev
vhdisk7
The same LUN is now exported to the client logical partition
from both Virtual I/O Server logical
partitions.
- AIX can
now be installed on the client logical partition. For instructions
on installing AIX,
see Installing AIX in
a Partitioned Environment in the IBM® Power Systems™ and AIX Information Center.
- After you have installed AIX on the client logical
partition, check for MPIO by running the following command:
lspath
You
see results similar to the following:
Enabled hdisk0 vscsi0
Enabled hdisk0 vscsi1
If one of the Virtual I/O Server logical partitions
fails, the results of the lspath command look similar
to the following:Failed hdisk0 vscsi0
Enabled hdisk0 vscsi1
Unless a health check is enabled,
the state continues to show Failed even after the
disk has recovered. To have the state updated automatically, type chdev
-l hdiskx -a hcheck_interval=60 -P. The client logical
partition must be rebooted for this change to take effect.