You can configure the storage policy copy as a parallel copy to optimize the use of storage media, and decrease the time needed to run an Auxiliary Copy operation.
When an Auxiliary Copy job is run, a parallel copy generates multiple secondary copy jobs, concurrently, based on the number of parallel copies configured in the storage policy. That is, the data is read from the source copy (only once) and written to the multiple storage policy copies. Therefore, multiple copies are written in parallel by reading the source media only once.