【筆記】Hadoop名詞解釋

名詞	意思	備註
metrics	HDFS與MapReduce daemon會收集一些與事件以及量測相關的資訊，這些總稱為metrics	例如，datanode會收集已寫入的byte數、已複製的block總數等metrics
data locality optimization	Hadoop在執行map task時，會盡全力將該task放到存放輸入該task資料的那台node去執行，以免使用到寶貴的頻寬進行資料的傳送
shuffle	A proccess by which the system performs the sort and transfers the map outputs to the reducers as inputs.
speculative execution	Hadoop doesn't try to diagnose and fix slow-running tasks; instead, it tries to detect when a task is running slower than expected and launches another equivalent task as a backup.