Explain the concept of consensus in distributed systems (e.g., Paxos, Raft).

Consensus is a fundamental problem in distributed systems that involves getting all the nodes in a group to agree on a single value. It is a challenging problem because nodes can fail or the network can be unreliable.

Paxos and Raft are two of the most well-known consensus algorithms. They are designed to be fault-tolerant and are used in many real-world distributed systems.

How do distributed file systems like HDFS ensure reliability and scalability?

HDFS (Hadoop Distributed File System) ensures reliability and scalability in the following ways:

  • Reliability: HDFS is designed to be fault-tolerant by replicating data across multiple nodes. By default, each block of data is replicated three times. If a node fails, the data can still be accessed from the other replicas.
  • Scalability: HDFS is highly scalable. It can be scaled out by adding more nodes to the cluster. This allows it to store and process massive amounts of data.