HP Hitachi Dynamic Link Manager Software - Manual (Page 55)

When you turn the intermittent error monitoring function off, information
about paths not subject to automatic failback will be reset. If you do not
want to reset the information about paths not subject to automatic
failback when you turn the intermittent error monitoring function off,
change the target paths to Offline(C).
#2
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 cannot be detected unless an I/O
operation is performed, because the system only checks the status of a path
when an I/O operation is performed. With path health checking, however, the
system can check the status of all online paths at regular intervals regardless
of whether I/Os operations are being performed. If an error is detected in a
path, the path health checking function switches the status of that path to
Offline(E) or Online(E). 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 6-15 .
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.
HDLM Functions
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Hitachi Dynamic Link Manager User Guide for Linux ®