Yes, you would create /data/db
at root. The MongoDB Documentation suggests the following command for creation on OS X mkdir -p /data/db
.
Regarding your second question, also yes. Since the Mongo Daemon failed to start and isn't listening you get the connection error.
MongoDB defaults to /data/db
for the data directory. You can override the default using the --dbpath
option on the mongod
command (also on the doc link above).