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Sharding is a data management technique that involves partitioning a database or blockchain into smaller, more manageable pieces called shards. Each shard operates as an independent entity that stores a subset of the total data.
Distributing data across multiple shards helps improve performance and scalability by ensuring that data operations can be carried out in a timely manner. This is particularly valuable for scenarios in which the volume of data surpasses the capacity of a single server or blockchain network node to handle operations effectively.
While sharding offers numerous benefits, it also comes with challenges, including potential difficulties with cross-shard transactions.
Database Sharding vs. Blockchain Sharding
Database sharding and blockchain sharding share the same underlying concept of dividing data into smaller parts to improve performance and scalability, but they are implemented in different contexts and have specific characteristics that differentiate them.
| Database Sharding | Blockchain Sharding | |
|---|---|---|
| Purpose | Scaling large centralized databases. | Scaling decentralized blockchain networks. |
| Data Distribution | Distributes data across multiple servers/nodes. | Distributes data across multiple blockchains. |
| Control | Centralized control through a database management system (DBMS). | Decentralized control governed by consensus mechanisms. |
| Inter-Shard Communication | Made easier because of centralized control. | Requires complex cross-shard communication mechanisms. |
Database Sharding
Database sharding is a technique used in database management systems (DBMSes) to improve scalability and performance by dividing a large database into smaller partitions that can be stored on a separate server or server cluster. Each shard typically contains a subset of the data and is identified by a shard key.
Database sharding is often used for situations in which there’s a need to handle a high volume of concurrent requests and the database has become too large to be efficiently managed by a single server.
By spreading the data out over multiple servers, each server or server cluster only has to manage a subset of the total transaction load. A central component or routing mechanism directs queries to the appropriate shard.
Horizontal Sharding vs. Vertical Sharding
Database sharding can be carried out horizontally or vertically.
Horizontal sharding (also called range sharding) focuses on distributing rows of data. Because it retains the same schema across all shards, horizontal sharding is a more straightforward approach for many applications.
In contrast, vertical sharding focuses on distributing database columns or tables. Although vertical sharding can be effective when different database columns or tables have very different access patterns, it can introduce a layer of complexity that needs to be managed carefully.
For example, JOIN operations spanning different shards might need to be managed at the application layer.
Blockchain Sharding
Blockchain sharding is a technique used to improve the scalability and performance of a blockchain network by dividing the blockchain into smaller partitions.
Breaking a blockchain into multiple shards reduces the computational burden on the network and allows more transactions to be processed in a given period of time. The exact details for how to shard a blockchain can vary based on the specific blockchain protocol that is being used.
Projects that are experimenting with sharding to improve scalability include:
- Ethereum
Sharding is being looked at as a way to horizontally scale out the Ethereum blockchain. The concept plays a very important role in The Surge (Ethereum 2.0).
While the Ethereum Foundation has not yet decided exactly which approach to sharding will be used in Ethereum 2.0, is likely that both Beacon Chains and Danksharding will be used to reduce gas fees and optimize smart contracts and dApp performance.
Danksharding will be used to improve the scalability and efficiency of the Ethereum network by dividing the Ethereum state into multiple shards, and Beacon Chains will be responsible for coordinating the shards and ensuring that all shards are synchronized.
- Polkadot
Polkadot uses a sharding mechanism called parachains to scale the network. A parachain is an individual blockchain that runs in parallel with other parachains within the same network. Each parachain is specialized and optimized for a particular use case or application.
Polkadot allows multiple parachains to operate concurrently, processing transactions and executing smart contracts independently. Polkadot uses a central relay chain to manage parachains and ensure their secure interaction.
The relay chain acts as a hub that coordinates communication and consensus between different parachains, and maintains the overall network security and interoperability while allowing the parachains to operate autonomously.
- Cosmos
Cosmos uses a sharding-like mechanism called “zones” to scale the network. Each zone functions as its own blockchain with its own consensus mechanism, smart contracts, and governance rules. The Cosmos Hub, which connects and coordinates communication between zones, uses the Inter-Blockchain Communication (IBC) protocol to enable secure data and asset transfers.
IBC allows zones to communicate with each other and transfer tokens and data between them. This makes it possible to build applications that span multiple zones.
