HP Hitachi Dynamic Link Manager Software Licenses - Manual (Page 39)

Figure 2-8 Flow of I/O Data When the Load Balancing Function Is Used
When the load balancing function is used, I/O operations are distributed via
multiple paths (A, B, C, and D). This helps to prevent problems with system
performance and helps prevent bottlenecks from occurring.
Paths To Which Load Balancing Is Applied
This subsection describes, for each type of storage system, the paths to
which the load balancing function is applied.
When Using the Thunder 9500V Series, or Hitachi AMS/WMS series
HDLM performs load balancing between owner paths or between non-owner
paths. An owner path is a path that passes through the CHA. This path is set
on the owner controller of the storage system LU. Since the owner controller
varies depending on the LU, the owner path also varies depending on the LU.
A non-owner path is a path that uses a CHA other than the owner controller
(a non-owner controller). Paths used for load balancing are selected from
owner paths first, then non-owner paths. To prevent performance in the
entire system from deteriorating, HDLM does not perform load balancing
between owner paths and non-owner paths. When some owner paths cannot
be used due to a problem such as a failure, load balancing is performed
HDLM Functions
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Hitachi Dynamic Link Manager (for Linux®) User Guide