Monday, 29 August 2011

Configuring Multi-Path I/O for AIX client logical partitions


Scenario: Configuring Multi-Path I/O for AIX client logical partitions

Multi-Path I/O (MPIO) helps provide increased availability of virtual 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.
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.
An illustration of an MPIO configuration with two Virtual I/O Server logical partitions.
Using the preceding figure as a guide, follow these steps:
  1. Using the HMC, create SCSI server adapters on the two Virtual I/O Server logical partitions.
  2. 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.
  3. On either of the Virtual I/O Server logical partitions, determine which disks are available by typinglsdev -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, we selected hdisk5.
  4. 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), so we determine the physical identifier (PVID) by running the lspv hdisk5command. 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.
  5. List the attributes of the disk using the lsdev command. In this scenario, we typed 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 typingchdev -dev hdiskx -attr reserve_policy=no_reserve.
  6. 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 Serverlogical partitions might vary.
  7. Determine if the reserve_policy attribute is set to no_reserve using the lsdev command. In this scenario, we typed 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.
  8. 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, we type the following commands:
    • On the first Virtual I/O Server logical partition, we typed mkvdev -vdev hdisk5 -vadapter vhost5 -dev vhdisk5
    • On the second Virtual I/O Server logical partition, we typed 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.
  9. AIX can now be installed on the client logical partition. 
  10. 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.

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