Back to course home
Anatomy of a Read Operation
HDFS read process
HDFS read process can be outlined as follows:
- When a file is opened for reading, HDFS client initiates a read request, by calling the
open()method of the
Distributed FileSystemobject. The client specifies the file name, start offset, and the read range length.
Distributed FileSystemobject calculates what blocks need to be read based on the given offset and range length, and requests the locations of the blocks from the NameNode.
- NameNode has metadata for all blocks' locations
Like the course? Get enrolled and start learning!