System maintenance operations such as updating operating systems, and applying security patches or hotfixes are routine operations in any data center. DataNodes undergoing such maintenance operations can go offline for anywhere from a few minutes to several hours. By design, Apache Hadoop HDFS can handle DataNodes going down. However, any uncoordinated maintenance operations on several DataNodes at the same time could lead to temporary data availability issues. HDFS currently supports the following features for performing planned maintenance activity:
The rolling upgrade process helps to upgrade the cluster software without taking the cluster offline.