# File lib/fog/aws/requests/efs/create_file_system.rb, line 25
        def create_file_system(creation_token, options={})
          response = Excon::Response.new

          id = "fs-#{Fog::Mock.random_letters(8)}"
          file_system = {
            "OwnerId"              => Fog::AWS::Mock.owner_id,
            "CreationToken"        => creation_token,
            "PerformanceMode"      => options[:performance_mode] || "generalPurpose",
            "FileSystemId"         => id,
            "CreationTime"         => Time.now.to_i.to_f,
            "LifeCycleState"       => "creating",
            "NumberOfMountTargets" => 0,
            "SizeInBytes"          => {
              "Value"     => 1024,
              "Timestamp" => Time.now.to_i.to_f
            }
          }

          self.data[:file_systems][id] = file_system
          response.body = file_system
          response.status = 201
          response
        end