...Runs anywhere from Linux to web browsers and Xen unikernels. Allows the users to define custom merge functions, use in-memory transactions (to keep track of reads as well as writes) and to define event-driven workflows using a notification mechanism. You can use Irmin on top of your own storage layer.
A linux userspace shadow (file data is on disk) relational filesystem (aka "database filesystem") using fuse and postgresql to store metadata. Directories can be queries, and powerful features (e.g. bayesian classification) are added through plugins