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Load balancing

By default, DMP uses the balanced path mechanism to provide load balancing across paths for Active/Active, A/P-C, A/PF-C and A/PG-C disk arrays. Load balancing maximizes I/O throughput by using the total bandwidth of all available paths. Sequential I/O starting within a certain range is sent down the same path in order to benefit from disk track caching. Large sequential I/O that does not fall within the range is distributed across the available paths to reduce the overhead on any one path.

For Active/Passive disk arrays, I/O is sent down the primary path. If the primary path fails, I/O is switched over to the other available primary paths or secondary paths. As the continuous transfer of ownership of LUNs from one controller to another results in severe I/O slowdown, load balancing across paths is not performed for Active/Passive disk arrays unless they support concurrent I/O.

Both paths of an Active/Passive array are not considered to be on different controllers when mirroring across controllers (for example, when creating a volume using vxassist make specified with the mirror=ctlr attribute).

For A/P-C, A/PF-C and A/PG-C arrays, load balancing is performed across all the currently active paths as is done for Active/Active arrays.

You can use the vxdmpadm command to change the I/O policy for the paths to an enclosure or disk array.

See "Specifying the I/O policy" on page 159.