Google Summer of Code (GSoC), a global program focused on introducing students to open source software development is nearing the end of its competition for this year. A student developer named Victor Perevertkin has been successful in his GSoC 2018 project on Btrfs file-system support for ReactOS. He has been able to boot the Windows API/ABI compatible OS off Btrfs.
For his GSoC 2018 project, Perevertkin has been working on Btrfs support within the ReactOS boot-loader as well as other fixes needed to allow for ReactOS to be installed on and boot from a Btrfs file-system.
BTRFS is case-sensitive file system, so paths like /ReactOS/System32, /reactos/system32, /ReactOS/system32 are different here. However, Windows is written assuming that case does not matter during path lookup. This issue is solved in WinBtrfs driver, but for Freeloader it can be a bit tricky.
After Perevertkin was done with the Freeloader development and had fixed the VirtualBox bug, he was able to get to first error message from btrfs-booted ReactOS. He later found out that this was due to a bug in WinBtrfs driver. A pull-request to the upstream repository with a bugfix is provided on GitHub repository.
At present, ReactOS is able to boot from BTRFS partition and also is in quite stable state. However, some problems are yet to be addressed.
Read about this news in detail on ReactOS Blog.