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NetBSD feature end-of-life announcement: soft dependencies

Soft dependencies, also known as soft updates or softdep, is a method of
maintaining file system integrity across an unscheduled system shutdown.  It
improves file system performance by allowing metadata writes to the file
system to take place asynchronously.  Soft dependencies was introduced with
NetBSD 1.5.

The upcoming 5.0 release of NetBSD will include an alternative technology
contributed by Wasabi Systems Inc.: Write Ahead Physical Block Logging, or
logging.  Logging will provide a feature set and performance profile
superior to soft dependencies.  One compelling advantage is that file
systems using it need not be checked with the fsck utility after an
unscheduled system shutdown.

In NetBSD 5.0 both soft dependencies and an experimental, preview
implementation of logging will be available.  From NetBSD 6.0 onwards, soft
dependencies will no longer be shipped as part of the system and logging
will be the preferred method of maintaining file system integrity with FFS
file systems.


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