A general-purpose file system for secondary storage

The need for a versatile on-line secondary storage complex in a multiprogramming environment is immense. During on-line interaction, user-owned off-line detachable storage media such as cards and tape become highly undesirable. On the other hand, if all users are to be able to retain as much information as they wish in machine-accessible secondary storage, various needs become crucial: Little-used information must percolate to devices with longer access times, to allow ample space on faster devices for more frequently used files. Furthermore, information must be easy to access when required, it must be safe from accidents and maliciousness, and it should be accessible to other users on an easily controllable basis when desired. Finally, any consideration which is not basic to a user's ability to manipulate this information should be invisible to him unless he specifies otherwise.