Operating Environment Requirements

• In SAN Boot mode, the virtual LUN running the host's operating system must be a common virtual LUN. You can change a common virtual LUN to a HyperMetro virtual LUN only after ODM is installed on the host and the host is restarted.
• When NPIV coupled with VIOS is used, the requirements of NPIV on hardware and software must be met.

• If AIX SAN Boot is used, the recommended configuration procedure is as follows:

  1. Use a single path to install the AIX SAN Boot system and start the operating system through a single-path disk.
  2. Install the multipathing software, restart the host for the multipathing software to take effect, and take over the SAN Boot disk.
  3. Finally, connect multiple paths.

Installing and Enabling Multipathing Software

AIX native MPIO can take over Huawei storage disks only if the AIX ODM package has been installed. After AIX ODM has been installed, the fc_err_recov and dyntrk parameters of the FC HBAs must be set. For details on how to install AIX ODM, see the AIX ODM for MPIO User Guide.

Run the following command to verify that MPIO has taken over the disks from Huawei storage.

Figure 6-6 MPIO takeover

Configuring Multipathing Software

The default I/O policy is fail_over. I/Os can be delivered only on one path. To deliver I/Os on multiple paths on a controller, run the following command to change the I/O policy to round_robin. In UltraPath 31.0.2 and later, the default path selection algorithm of AIX ODM for MPIO is changed from fail_over to round_robin.

• When native MPIO is used, services must be suspended before you change the I/O policy for hdisk.
• In AIX 6.1 TL9 and later or AIX 7.1 TL5 and later, if the disk type is not SCSI-2 reserves, use the shortest_queue path selection algorithm to maximize SAN resource usage. When the load is light, the shortest_queue algorithm is similar to the round_robin algorithm. Once a path is congested, the system automatically allocates more I/Os to other lightly loaded paths. The queue_depth parameter can be modified based on the customer's host service configurations.

bash-3.2# chdev -l hdisk1 -a algorithm=round_robin
hdisk1 changed
bash-3.2# lsattr -EHl hdisk1
attribute       value              description                      user_settable

PCM             PCM/friend/MPIOpcm Path Control Module              False
PR_key_value    none               Persistant Reserve Key Value     True
algorithm       round_robin        Algorithm                        True
clr_q           no                 Device CLEARS its Queue on error True
dist_err_pcnt   0                  Distributed Error Percentage     True
dist_tw_width   50                 Distributed Error Sample Time    True
hcheck_cmd      test_unit_rdy      Health Check Command             True
hcheck_interval 30                 Health Check Interval            True
hcheck_mode     nonactive          Health Check Mode                True
location                           Location Label                   True
lun_id          0x1000000000000    Logical Unit Number ID           False
lun_reset_spt   yes                LUN Level Reset                  True
max_transfer    0x40000            Maximum TRANSFER Size            True
node_name       0x2100010203040509 FC Node Name                     False
pvid            none               Physical volume identifier       False
q_err           yes                Use QERR bit                     True
q_type          simple             Queuing TYPE                     True
queue_depth     32                 Queue DEPTH                      True
reassign_to     120                REASSIGN time out value          True
reserve_policy  no_reserve         Reserve Policy                   True
rw_timeout      30                 READ/WRITE time out value        True
scsi_id         0x10400            SCSI ID                          False
start_timeout   60                 START unit time out value        True
timeout_policy  fail_path          Timeout Policy                   True
ww_name         0x2991010203040509 FC World Wide Name               False
bash-3.2#