New Storage System
<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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