See if you can find anything useful here.
libhammer is an attempt to collect the most basic functions to interact with the HAMMER filesystem.
hammer-backup would be a backup system based upon HAMMER FS snapshots.
iSCSI is a section with all the related information about iSCSI protocol and DragonFly BSD.
dirfs is a userland filesystem for vkernel that provides the ability to mount any host directory.
Final goal is to be able to dirfs root mount for vkernel.