Abstract: A method and system for characterizing data storage usage by a host in a data storage system that provides a host-specific access area in a storage device. Access is gained to the access area and blocks of data from the access area are retrieved and stored in buffers. The stored data is classified as allocated as an organized data structured defined by a particular file system or non-typical system. The classifying includes sequentially mapping the data into file system data structures until a match is obtained and then the mapped data structure is stored. The match is verified by retrieving expected values for a file system and comparing the mapped values with the expected values. The mapped data is used to determine host storage information, such as number of blocks, number of the used data blocks, free space, number of files, location of files, and size of files.