A data storage subsystem employs managed files, each comprising one or an aggregation of multiple individual, constituent user files, to reduce
file management overhead costs. After receiving user files from a
client station, the subsystem creates a contiguous managed file by aggregating selected ones of the received user files according to certain predetermined criteria. Managed file creation and use are transparent to the
client stations. To aid in
file management, the subsystem provides a mapping table that lists, for each user file, a corresponding location of that user file within a managed file. With this hardware and table structure, the
system conducts
file management with reduced overhead. For example, internal
data management operations include an improved copy operation where a managed file is copied as a contiguous unit between first and second locations in the data storage subsystem. In addition to internal
data management operations, the subsystem satisfies
client output requests, including retrieve operations initiated when the subsystem receives a retrieval request and identified user file from a
client station. In response, the subsystem employs the mapping table to find the identified user file's location in the managed file. Referencing the identified user file's location in the managed file enables the subsystem to obtain a copy of the identified user file, which is ultimately provided to the requesting
client station.