This patch value is in the following:
1. In the Storage-Backup environment of HyperCluster, includes
one storage array near to the host and one remote storage array,
and the two storage arrays have the same hardware.The same LUN is
writed or readed by the two storage arrays. However, usually, the
libmultipath/prioritizers: Prioritizer for device mapper multipath,
where the corresponding priority values of specific paths are provided
by a latency algorithm. And the latency algorithm is dependent on the
following arguments(latency_interval and io_num).
The principle of the algorithm is
