Methods, systems, and apparatus, including computer program products, for creating test directories and files in a logical storage in a data storage system. The directories include a root directory subdirectories in the root directory. Each directory has a directory key name that has a prefix value; a subdirectory value, the subdirectory value defining a number of immediate subdirectories in the directory; a subdirectory prefix value, the subdirectory prefix value defining a prefix value of each directory key name of each immediate subdirectory in the directory; and a file value, the file value defining a number of files stored in the directory. The contents of any directory can be checked against the directory key name to determine if a data storage error has occurred during testing.