Cassandra is a distributed non-relational database that can handle large chunks of unstructured data sets across many commodity servers. It’s a popular choice for large-scale enterprise applications that require high availability and scalability across distributed systems.
What Is Cassandra?
Cassandra is an open-source, distributed NoSQL database designed to manage large volumes of structured and unstructured data across multiple servers. It offers high availability, fault tolerance and horizontal scalability without a single point of failure.
Thanks to Cassandra’s distributed nature, there is no single point of failure. Instead, the data lives in many replica nodes throughout the database. If a node fails, the system continues to operate without data loss due to its use of replica nodes.
How Does Cassandra Work?
Cassandra is designed to manage massive volumes of distributed data across cloud or on-premises infrastructures. In case of data loss or failure in one of the nodes, the data throughout the rest of the system remains safe due to Cassandra’s distributed nature. This resilience is enabled by Cassandra’s replication architecture.
Cassandra Key Components
Cassandra has three key components that help it operate: its architecture, partitioning system and replicability.
Let’s take a look at each of these components.
1. Cassandra Architecture
Cassandra’s architecture is a peer-to-peer, shared-nothing system, where each node independently handles part of the data and query load. Each node in the Cassandra database has an equal amount of importance, which is the key aspect of Cassandra’s reliable structure.
A single Cassandra node is responsible for storing data and a group of these nodes is called a data center. These data centers combined form a cluster that is responsible for processing the data.
Even when you run out of space, Cassandra’s structure makes it simple to add more storage. To expand storage capacity, developers can add new nodes, and Cassandra will automatically redistribute data across them through a process called rebalancing. This process also goes the other direction: A developer can scale the system down by decommissioning nodes, which helps optimize resource use and reduce operational costs.
Cassandra’s architecture gives it an advantage over SQL databases when it comes to housing data. While Cassandra allows for seamless horizontal scaling by adding nodes, many traditional SQL databases require more complex setups to scale without downtime.
2. Cassandra Partitioning System
Cassandra’s partitioning system determines how data is distributed across nodes using a consistent hashing algorithm and a partition key.
Each node in the database holds a token based on the partitioning key, which helps the system locate the data. When a client connects with the database, a coordinator node ensures the data gets to the right node. This happens with the help of the nodal tokens and a hash function of the partition key.
3. Cassandra Replicability
Another key function of Cassandra is replicating data to replica nodes. This feature makes the database less susceptible to data loss.
Cassandra uses the replication factor (RF) to specify the number of replicas to create. For example, an RF of three means there are three replicas for each data node.
This is the key to Cassandra’s reliability. If one node stops functioning, the data still exists in the replica nodes and you’re unlikely to ever lose data completely.
Frequently Asked Questions
What is Cassandra?
Cassandra is an open-source, distributed NoSQL database designed to handle large amounts of unstructured data across multiple servers. It provides high performance, scalability and fault tolerance capabilities.
How does Cassandra work?
Cassandra works by using a peer-to-peer cluster of nodes that store and process data. Each node is equally important, and data is replicated across multiple nodes to prevent a single point of system failure.
What makes Cassandra scalable?
Cassandra’s architecture allows developers to add or remove nodes without downtime. When new nodes are added, data is redistributed, making it easy to expand storage and processing capacity.
