1. A method for prestaging data into cache from a storage system in preparation for data transfer operations, wherein a first processing unit communicates data transfer operations to a second processing unit that controls access to the storage system, comprising the first processing unit: determining addressable locations in the storage system of data to prestage into cache; generating a data structure capable of indicating contiguous and noncontiguous addressable locations in the storage system including the data to prestage into the cache; transmitting a prestage command to a second processing unit which controls access to the storage system, wherein the prestage command causes the second processing unit to prestage into cache the data at the addressable locations indicated in the data structure; and requesting data at the addressable locations indicated in the data structure, wherein the second processing unit returns the requested data from the cache.