HiCommand Dynamic Link Manager User's Guide (for Windows(R))

2.6.1 Paths to which load balancing is applied

This subsection describes, for each storage subsystem, the paths to which the load balancing function is applied.

Organization of this subsection

(1) When using the Thunder 9200 Series, Thunder 9500V Series, or TagmaStore AMS/WMS series

(2) When using the Lightning 9900 Series, Lightning 9900V Series, TagmaStore USP or Universal Storage Platform V

(1) When using the Thunder 9200 Series, Thunder 9500V Series, or TagmaStore 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 channel adapter. This path is set on the owner controller of the storage subsystem LU. When you set an LU, you determine the owner controller and non-owner controller for the 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 channel adapter other than the owner controller (a non-owner controller). 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 no owner paths can be used, load balancing is performed among the non-owner paths.

For the example in Figure 2-9 Overview of load balancing, suppose that the owner controller of LU0 is CHA0. When the LU is accessed, the load is balanced between the paths (A) and (B) (that is, between owner paths). When the path (A) cannot be used due to a problem such as a failure, the LU can only be accessed via the path (B). When the paths (A) and (B)cannot be used, the load is balanced between the paths (C) and (D) (that is, between non-owner paths).

Figure 2-9 Overview of load balancing

(2) When using the Lightning 9900 Series, Lightning 9900V Series, TagmaStore USP or Universal Storage Platform V

All the online paths are owner paths. Therefore, for the example in Figure 2-8 I/O flow when the load balancing function is being used, when the LU is accessed, the load is balanced among the paths(A), (B), (C), and (D). When one of the paths cannot be used due to a problem such as a failure, the load is balanced among the remaining paths.

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