I use an old machine as a file server, for backups, and as a testbed for development. I currently have Debian installed, but I'm very interested in FreeBSD because of ZFS: I really, really like its file integrity features.
Before I switch, however, I wanted to ask: what's the best way to migrate my ~400GB of files from the current filesystem (ext3) to ZFS? My number-one requirement is that the migration be absolutely reliable: I don't want to lose any data. (I'll be backing it up before doing this anyway, but still.) My secondary goal is speed: I'd rather not have this take overnight if it doesn't have to.
Recommendations? Is FUSE for FreeBSD stable enough to use? What about FreeBSD's native read support for ext3? NFS, maybe? How have you done this?