What does block mean?

Smallest consistent location on your hard drive where information is stored is known as a block. HDFS stores each document as blocks, and appropriate it over the Hadoop cluster. The default size of a square in HDFS is 128 MB (Hadoop 2.x) and 64 MB (Hadoop 1.x), which is considerably bigger when contrasted with the Linux system where the block size is 4KB. The reason of having this enormous square size is to limit the cost of look for and diminish the Meta information data created per block.