HP XP Racks - Manual (Page 48)

The number of errors and the time passed since error monitoring had
started are both reset to 0, and then monitoring restarts from the time
the setting change is made in accordance with the changed monitoring
conditions.
#3
The number of errors and the time passed since error monitoring had
started are both reset to 0, and then monitoring restarts from the time
the HDLM manager starts.
Detecting errors by using path health checking
HDLM can check the status of paths for which I/O operations are not being
performed at regular intervals. This function is called path health checking.
Without path health checking, an error is not detected unless I/O is
performed because the system only checks the path status when I/O is
performed. With path health checking, however, the system checks the status
of online paths at regular intervals regardless of whether I/O is performed. If
an error is detected in a path, path health checking functionality switches the
status of that path to Offline(E) or Online(E), so you can use the dlnkmgr
command's view operation to check the path error.
For example, in a normal state, I/O operations are not performed on the
paths coming from the standby host in the cluster configuration or on non-
owner paths (that is, some of the paths that access a Thunder 9500V series,
or Hitachi AMS/WMS series storage system). Because of this, for the standby
host or for a host connected to non-owner paths, we recommend that you
use path health checking to detect errors. This enables the system to use the
most up-to-date path-status information when selecting the next path to use.
You can configure path health checking by executing the dlnkmgr command's
set operation. For details on the set operation, see
set (Sets Up the
Operating Environment) on page 6-16 .
Distributing a Load by Using the Dynamic I/O Path Control
Function
The result of using HDLM load balancing to distribute a load can be improved,
by applying the HDLM dynamic I/O path control function to the storage
system in which the dynamic load balance control function is installed.
What is the Dynamic Load Balance Control Function
In a system configuration in which multiple hosts and a storage system are
connected, the I/O processing load tends to concentrate on the controller of
the storage system, causing throughput performance of the entire system
decrease. The dynamic load balance controller function evaluates such load
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HDLM Functions
Hitachi Dynamic Link Manager User Guide for AIX®