GEFS is a crash-safe, snapshotting, corruption-detecting, simple, and reasonably fast file system. It's built on a write-optimized data structure known as a Bε tree. Originally developed for Plan 9, and shipped on 9Front in 2024, it is now in production use. It runs 9Front build infrastructure, some web servers, and is in wide use among 9Front users. Few of them claim to have been on mind altering substances when they made this decision. A version of it is in progress for OpenBSD. It's ready to destroy your data. In this talk, the speaker will describe the user facing features of GEFS. They'll talk about how the data structures work internally. That will be followed by a discussion of how this connects to the VFS layer in OpenBSD, and finally, will wrap up with a summary of what's still broken. The speaker has been using this file system on their Plan 9 laptop for over a year at this point, and has only lost other people's data. p.s. It's pronounced with 'G' as in 'GIF'