# File lib/backup/syncer/cloud.rb, line 72
        def sync!(mirror = false, concurrency_type = false, concurrency_level = 2)
          block = Proc.new { |relative_path| sync_file relative_path, mirror }

          case concurrency_type
          when FalseClass
            all_file_names.each &block
          when :threads
            Parallel.each all_file_names, :in_threads => concurrency_level, &block
          when :processes
            Parallel.each all_file_names, :in_processes => concurrency_level, &block
          else
            raise "Unknown concurrency_type setting: #{concurrency_type.inspect}"
          end
        end