Cassandra Architecture Tutorial
1. Introduction to Cassandra
Cassandra is a distributed NoSQL database designed to handle large amounts of structured data across many commodity servers. It provides high availability with no single point of failure. It is highly scalable, allowing for the addition of new nodes without downtime.
2. Key Components of Cassandra Architecture
Understanding Cassandra architecture is crucial for effective utilization. The main components include:
- Node: A single instance of Cassandra running on a machine.
- Cluster: A collection of nodes that work together. The nodes in a cluster share the same keyspace.
- Data Center: A group of nodes within a cluster. Data centers can be located in different geographical regions.
- Partition: A set of data that is distributed across nodes. Each partition is identified by its partition key.
- Replication: The process of storing copies of data on multiple nodes to ensure reliability.
- Commit Log: A log file that records all changes to the database, which helps in recovery.
- Memtable: An in-memory data structure where data is written before it is flushed to disk.
- SSTable: A persistent data file that stores the data on disk after it is flushed from the memtable.
3. Data Distribution and Replication
Cassandra uses a unique approach to data distribution and replication. The data is divided across the nodes in a cluster using a consistent hashing mechanism.
Example of Data Distribution:
When you insert a record, Cassandra determines which node will store the data based on the partition key. This ensures that data is evenly distributed across the nodes.
Replication is managed through replication strategies:
- SimpleStrategy: Suitable for a single data center.
- NetworkTopologyStrategy: Designed for multiple data centers, allowing configuration of replication levels per data center.
4. Consistency and Availability
Cassandra follows the CAP theorem, providing consistency, availability, and partition tolerance. It allows developers to choose the consistency level depending on the use case.
Example of Consistency Levels:
- ONE: Only one replica must acknowledge the read/write operation.
- QUORUM: A majority of replicas must acknowledge the operation.
- ALL: All replicas must acknowledge the operation.
5. Conclusion
Cassandra's architecture is designed for scalability and reliability, making it suitable for applications that require high availability and performance. Understanding its components, data distribution, and consistency models is essential for leveraging its capabilities effectively.