<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)
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