# File lib/backup/syncer/cloud/base.rb, line 82
          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 Errors::Syncer::Cloud::ConfigurationError,
                  "Unknown concurrency_type setting: #{ concurrency_type.inspect }"
            end
          end