save to disk

Start a new IEX shell like so

 iex --sname dsktest  -S mix

paste the following in

Amnesia.Schema.create
Amnesia.start
Database.create( disk: [node])
Database.wait
use Amnesia
use Database
Amnesia.transaction! do
  user = User[id: 24]
  user.add_message("yo dawg i'm on disk")
  user.write
end
Amnesia.stop

exit iex, and start it back up again. Paste the following

Amnesia.start
use Amnesia
use Database
u = User.read!(24)
u.messages!

the result you want is:

iex(dsktest@ip-10-40-65-192)7> u.messages!
[Database.Message[user_id: 24, content: "yo dawg i'm on disk"]]