Edit: Turns out for what I'm trying to do (mount luks encrypted raid after start up) only needs the device mapping for the raid drive and not a file-system object.

So I luks encrypted the raid and call a script to open the vault and mount it when I need to.

In my system config file I added a raid drive like so:

(mapped-devices (list (mapped-device
                                     (source (uuid
                                                  "205e5caa-694f-4457-a2a1-8affa3536e75"))
                                     (target "guix")
                                     (type luks-device-mapping))

                                  (mapped-device
                                     (source (list "/dev/sdb1" "/dev/sdc1"))
                                     (target "/dev/md0")
                                     (type raid-device-mapping))))

(file-systems (cons* (file-system
                                  (mount-point "/")
                                  (device "/dev/mapper/guix")
                                  (type "ext4")
                                  (dependencies (list (list-ref mapped-devices 0))))

                               (file-system
                                  (mount-point "/mnt/nas")
                                  (device "/dev/md0")
                                  (type "ext4")
                                  (mount? #f)
                                  (dependencies (list (list-ref mapped-devices 1)))) %base-file-systems)))

I'd now like to luks encrypt the raid drive but I'm not sure how to go about doing it. Do I simply make a another mapped-device object, specifying the raid drive uuid and "/dev/md0" as the target:

(mapped-device
   (source (uuid
                {raid uuid}))
                (target "/dev/md0")
                (type luks-device-mapping))

and then pass that as a dependency to the raid file system object?

Thanks