Dragonfly BSD
DragonFly BSD - Features
The new DragonFly BSD Handbook

HAMMER is a file system written for DragonFly that provides instant crash recovery, multi-volume file systems, integrity checking, fine grained history/undo, networked mirroring, and historical snapshots. HAMMER is the default file system for DragonFly.

DragonFly Handbook (old)
A Quick Start on Dragonfly (old)

The DragonFly BSD Digest