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 makes extensive use of tokens as a synchronization mechanism; tokens are inherently deadlock-free and easily composable. The use of soft token locks results in less cross-subsystem pollution and more maintainable code, both of which allow us to parallelize the system with less effort compared to other kernels, which primarily use hard mutex locks. 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. The DragonFly storage stack comprises robust AHCI drivers, stable device names via DEVFS and a partial implementation of Device Mapper for reliable volume management and encryption. Some other features that are especially useful to system administrators are variant symlinks (i.e. symlinks that are resolved at runtime based on user-specific or system-wide variables) and a performant and scalable TMPFS implementation. Our system makes pervasive use of NULLFS mounts, which allow the administrator to make arbitrary parts of the filesystem hierarchy visible in other locations with virtually no overhead. A major crux of any open source operating system is third party applications. DragonFly leverages the pkgsrc system to provide thousands of applications in source and binary forms. These features and more band together to make DragonFly a modern, useful, friendly and familiar UNIX-like operating system. The DragonFly BSD community is made up of users and developers that take pride in an operating system that maintains challenging goals and ideals. This community has no reservation about cutting ties with legacy when it makes sense, preferring a pragmatic, no-nonsense approach to development of the system. The community also takes pride in its openness and innovative spirit, applying patience liberally and always trying to find a means to meet or exceed the performance of our competitors while maintaining our trademark algorithmic simplicity. For more information, visit the Features and History pages.

• published: 18 Aug 2013
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