Advanced POWER Virtualization on IBM System p5 - Previous ...

Note: The path switching also works even if the hcheck_interval attribute is
set to 0, but it is useful to have the status updated automatically.
Example 4-22 Changing the health check interval
# chdev -l hdisk0 -a hcheck_interval=60 -P
hdisk0 changed
# lsattr -El hdisk0
PCM PCM/friend/vscsi Path Control Module False
algorithm fail_over Algorithm True
hcheck_cmd test_unit_rdy Health Check Command True
hcheck_interval 60 Health Check Interval True
hcheck_mode nonactive Health Check Mode True
max_transfer 0x40000 Maximum TRANSFER Size True
pvid
00c7cd9eabdeaf320000000000000000 Physical volume identifier False
queue_depth 3 Queue DEPTH False
reserve_policy no_reserve Reserve Policy True
Note: MPIO on the client partition runs a fail_over algorithm. That means
only one path is active at a time. If you shut down a Virtual I/O Server that
serves the inactive path, then the path mode does not change to failed
because no I/O is using this path.
Failover may require a small period of time in which the client
re-establishes a path to the SAN. Testing of production workloads should
be made in order to establish if this delay is suitable.
5. Set the path priority for this partition to have the active path going over
VIO_Server2. The default setting is priority 1 on both paths, as shown in
Example 4-23. In this case, you do not need a special path and the system
will pick path0 as the active path. Priority 1 is the highest priority, and you can
define a priority from 1 to 255.
Example 4-23 Show path priority using lspath
# lspath -AHE -l hdisk0 -p vscsi0
attribute value description user_settable
priority 1 Priority True
# lspath -AHE -l hdisk0 -p vscsi1
attribute value description user_settable
priority 1 Priority True
Chapter 4. Setting up virtual I/O: advanced 231