When comparing DragonFly BSD vs illumos, the Slant community recommends illumos for most people. In the question“What are the best open-source Unix like operating systems?” illumos is ranked 4th while DragonFly BSD is ranked 5th. The most important reason people chose illumos is:
Illumos is completely free and open source.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Open Source
Illumos is completely free and open source.
Pro ZFS file system
illumos uses ZFS as its file system. ZFS is also a logical volume manager besides being a combines file system.
The main features of ZFS include: protection against data corruption, data compression, checking continuous integrity, high storage capacities support etc...
Pro Zones
Zones provide an isolated environment to run applications in. Processes that run in zones are prohibited to interfere or monitor any other activity in the system.
Pro Performance analysis and troubleshooting
illumos uses DTrace for performance analysis and troubleshooting.
Cons
Con The promise hasn't become a reality, despite years of development. Linux is still the pragmatic choice for production use.
File system and scale-ability are still under development, after many years.