What does hadoop do?

java language foundation is needed to provide mass data storage and calculation.

Hadoop implements a distributed file system (HDFS). It has the characteristics of high fault tolerance and is designed to be deployed on low-cost hardware. Moreover, it provides high throughput to access application data, which is suitable for those applications with large data set.

Features

1. Snapshot supports storing a copy of data at a specific time, and snapshot can roll back the failed cluster to a previous normal point in time. HDFS already supports metadata snapshots.

2. HDFS is designed to support large files. Programs running on HDFS are also used to process large data sets. These programs only write data once and read data requests one or more times, and these read operations are required to meet the streaming speed.

HDFS supports write once and read many times. The typical block size in HDFS is 64MB. An HDFS file can be divided into multiple blocks with the size of 64MB, and each block can be distributed on different data nodes if necessary.

3. Stage status: A client's request to create a file will not be immediately forwarded to the name node. In fact, at first, HDFS clients cache file data in local temporary files.