An apparatus and associated methodology for a data storage system having a data storage space operably transferring user data via input/output (I/O) commands between the data storage system and another device. The data storage space includes a first memory device operably storing location information for a selected user data set corresponding to one of the I/O commands. The first memory also operably stores a first amount of the selected user data set. The data storage space also includes a second memory device different than the first memory device and operably storing a different second amount of the selected user data set. The data storage system has a controller that interleaves an entirety of the selected user data set from the first and second memory devices during execution of another of the I/O commands.