DragonFly belongs to the same class of operating systems as other BSD-derived systems and Linux. It is based on the same UNIX ideals and APIs and shares ancestor code with other BSD operating systems. DragonFly provides an opportunity for the BSD base to grow in an entirely different direction from the one taken in the FreeBSD, NetBSD, and OpenBSD series. DragonFly includes many useful features that differentiate it from other operating systems in the same class. The most prominent one is HAMMER, our modern high performance filesystem with built-in mirroring and historic access functionality. Virtual kernels provide the ability to run a full-blown kernel as a user process for the purpose of managing resources or for accelerated kernel development and debugging. The kernel uses several synchronization and locking mechanisms for SMP. Much of the work done since the project began has been in this area. A combination of intentional simplification of certain classes of locks to make more expansive subsystems less prone to deadlocks, and the rewriting of nearly all the original codebase using algorithms designed specifically with SMP in mind, has resulted in an extremely stable, high-performance kernel that is capable of efficiently using all cpu, memory, and I/O resources thrown at it. DragonFlyBSD has virtually no bottlenecks or lock contention in-kernel. Nearly all operations are able to run concurrently on any number of cpus. Over the years, the VFS support infrastructure (namecache, vnode cache), user support infrastructure (uid, gid, process groups, sessions), process and threading infrastructure, storage subsystems, networking, user and kernel memory allocation and management, process fork, exec, and exit/teardown, time keeping, and all other aspects of kernel design have been rewritten with extreme SMP performance as a goal. DragonFly is uniquely positioned to take advantage of the wide availability of affordable Solid Storage Devices (SSDs), by making use of swap space to cache filesystem data and meta-data. This feature, commonly referred to as "swapcache", can give a significant boost to both server and workstation workloads, with a very minor hardware investment.