HP Hitachi Dynamic Link Manager Software - Manual (Page 41)

2. HDLM Functions
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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). The paths to be used
are selected, in the order of owner paths and 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 among the remaining
usable owner paths. When all owner paths cannot be used, load balancing is performed
among the non-owner paths.
For the example in Figure 2-7: Overview of Load Balancing, suppose that in the
owner controller of LU0 is CHA0. When the LU is accessed, the load is balanced
between the two physical paths A and B, which are both owner paths. When one of the
paths (A) cannot be used, then the LU is accessed from the only other owner physical
path (B). When both of the owner physical paths (A and B) cannot be used, the load is
then balanced between two other, non-owner physical paths (C and D).
Figure 2-7: Overview of Load Balancing