Source : Free On-Line Dictionary of Computing

New Storage System
     
         (NSS) A major {Multics} implementation project
        during the 1970s.  The initial Multics {file system} design
        had evolved from the one-huge-disk world of {CTSS}.  When
        multiple disk units were used they were just assigned
        increasing ranges of disk addresses, so a {segment} could have
        {pages} scattered over all disks on the system.  This provided
        good {I/O} {parallelism} but made {crash recovery} expensive.
        NSS redesigned the lower levels of the file system,
        introducing the concepts of {logical volume} and {physical
        volume} and a mapping from a Multics directory branch to a
        {VTOC} entry for each file.  The new system had much better
        recovery performance in exchange for a small space and
        performance cost.
     
        (1997-01-29)