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DocDB sharding layer

Learn about sharding strategies, hash and range sharding, colocated tables, and table splitting.

A distributed SQL database needs to automatically split the data in a table and distribute it across nodes. This is known as data sharding and it can be achieved through different strategies, each with its own tradeoffs. YugabyteDB's sharding architecture is inspired by Google Spanner.

Sharding

YugabyteDB splits table data into smaller pieces called tablets a.k.a shards. Sharding is the process of mapping of a row of a table to a shard. Sharding helps in scalability and geo-distribution by horizontally partitioning data. These shards are distributed across multiple server nodes (containers, virtual machines, bare-metal) in a shared-nothing architecture. The application interacts with a SQL table as one logical unit and remains agnostic to the physical placement of the shards. DocDB supports range and hash sharding natively.

To know more about the different sharding strategies and how they work, see Sharding strategies.

Tablet splitting

As table data grows, the size of tablets increase. Once a tablet reaches a threshold size, it automatically splits into two. These 2 new tablets can now be placed in other nodes to keep the load on the system balanced. Tablet splitting is one of the foundations of scaling.

To understand how and when tablets split, see Tablet splitting.

Cluster balancing

Cluster balancing is the process by which YugabyteDB automatically distributes data and queries across the nodes in a cluster to maintain fault tolerance and maximize performance. The cluster balancer continuously monitors the cluster configuration and moves tablet data and leaders to evenly distribute data and query load, thus distributing CPU, disk, and network load across the cluster. Cluster balancing automatically occurs when a cluster is scaled in or out, when there are node outages, and after creating or deleting tables and tablets.

To learn about cluster balancing scenarios and how to monitor its progress, see Cluster balancing.