A data storage caching architecture supports using native local memory such as host-based RAM, and if available, Solid State Disk (SSD) memory for storing pre-cache delta-compression based delta, reference, and independent data by exploiting content locality, temporal locality, and spatial locality of data accesses to primary (e.g. disk-based) storage. The architecture makes excellent use of the physical properties of the different types of memory available (fast r / w RAM, low cost fast read SSD, etc) by applying algorithms to determine what types of data to store in each type of memory. Algorithms include similarity detection, delta compression, least popularly used cache management, conservative insertion and promotion cache replacement, and the like.