storage (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)