Compute Node
- It's the computer or machine where you can execute actual business logic.
- It has two parameters RAM and CPU.
Storage Node
- It's the computer or machine to store the processing data where your file system resides
- Generally, the compute and storage nodes you can find at one location.
- It designates block storage.
Restrictions for Key and Value Class
- The key and value classes have to be serialized by the framework. To make them serializable Hadoop provides a Writable interface.
- As you know from the java itself that the key of the Map should be comparable, hence the key has to implement one more interface WritableComparable.
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