======================================================================================== = Please ensure that you set the default write concern for the database by setting = = one of the options = = = = w: (value of 1 or the string 'majority'), where < 1 means = = no write acknowlegement = = journal: true/false, wait for flush to journal before acknowlegement = = fsync: true/false, wait for flush to file system before acknowlegement = = = = For backward compatibility safe is still supported and...