When the system contains multiple paths to a single LU, HDLM can distribute the load across the paths by using multiple paths to transfer the I/O data. This function is called load balancing, and it prevents a single, heavily loaded path from affecting the performance of the entire system.
Note that some I/O operations managed by HDLM can be distributed to each path, while others cannot. Therefore, even though load balancing function is used, I/O operations might not be equally allocated to each path.
Figure 1 shows the flow of I/O data when the load balancing function is not used. Figure 2 shows the flow of I/O data when the load balancing function is used. Both figures show examples of I/O operations being issued for the same LU by multiple applications.
When the load balancing function is not used, I/O operations converge onto a single path (A). The load on that one path (A) will cause a bottleneck, which might cause problems with system performance.
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.