The concept of sharding and how it works

Blockchain technology brings unprecedented potential in terms of decentralization, transparency and security, but it also faces the huge challenge of scalability. Scalability is one of the blockchain trilemma, the other two being security and decentralization. The blockchain field has always strived to satisfy the above three items at the same time, and "sharding" is a strategic solution that can come in handy.

What is sharding?

Sharding is a concept borrowed from traditional database management and refers to the process of splitting a larger database into smaller, more manageable parts (called "shards"). Sharding is used in the blockchain field to improve scalability while maintaining the principle of decentralization. Sharding actually divides the blockchain network into smaller parts, and each sharded part can process transactions and smart contracts in parallel.

How does sharding work?

To understand how sharding is performed in a blockchain network, you need to first understand how blockchain data is conventionally stored and processed. There are many ways to process data. Sequential processing and parallel processing will be introduced below.

Generally speaking, each blockchain node is responsible for processing all transaction volume within the network. This type of data processing is called "sequential processing". That is, each node must maintain and store all critical information, such as account balances and transaction history. Essentially, each node must handle all network operations, data, and transactions.

This mode enhances the security of the blockchain by recording every transaction on all nodes, but it also greatly reduces the data processing speed. This is where data parallel processing comes into play, allowing multiple operations to be performed simultaneously.

Sharding splits or “partitions” the transaction workload across the entire blockchain network and is therefore an effective solution to this dilemma. This means that not all nodes need to manage or process the entire workload of the blockchain.

In contrast, sharding separates the workload through horizontal splitting. In this process, data is divided into horizontal subsets, with each shard acting as an independent database and able to process transactions separately from other shards.

Horizontal split and vertical split

Horizontal split and vertical split are the two main methods of database expansion. Both approaches are designed to efficiently manage large data sets, but the basics of how they operate are completely different. Sharding is a common way to implement split horizon.

Data can be divided into rows and distributed to different nodes (or databases) through horizontal splitting. Each node (or database) contains a subset of data. Each row within the table is a unique entity, so separate rows do not compromise data integrity. A classic example of split horizon is the distribution of blockchain networks such as Ethereum and Bitcoin.

Vertically split data is divided into columns instead of rows. Each partition of a vertical split contains data for individual entities or a subset of the entire dataset, but only for a specific set of attributes. For example, a customer table with columns such as Name, Status, Description, and Photo. In the case of vertical splitting, "name" and "status" might be stored in one table, and "description" and "photo" in another table.

Why is horizontal splitting more popular?

In blockchain networks, horizontal partitioning is usually preferred over vertical partitioning, mainly for the three main reasons of scalability, decentralization and security.

Scalability: Sharding provides a solution by breaking down data into smaller more manageable “shards”. Each shard can run independently and process more transactions simultaneously, increasing network speed and efficiency. Vertical splitting distributes columns across different databases, which can make retrieving full transaction or block information more complex, limiting scalability.

Decentralization: Consistent with the core concept of blockchain, split horizon supports decentralization. If nodes only need to process a portion of the total data (one shard), the computational and storage load will be reduced, allowing more nodes to participate in the network. In contrast, vertical partitioning has the limitation that each node needs to access all partitions (all data columns) to understand and verify the complete block data.

Security & Data Integrity: Each shard (or partition) contains complete transaction data to ensure each node contains a complete and accurate copy of its portion of the blockchain, so split horizon maintains data integrity . Vertical segmentation essentially splits the block data of different nodes, which makes it difficult to ensure the most important data integrity and security of the blockchain network.

What are the advantages of sharding?

The potential advantages that sharding brings to blockchain technology will be explored in detail below:

Improving transaction speed: Sharding promotes parallel processing of transactions. Instead of processing transactions one by one in sequence, sharding allows transactions to be processed simultaneously on different shards. Each shard operates independently, significantly increasing transaction speed. This not only speeds up transactions, it also means that the entire network can handle more users, thus promoting the popularity of the network.

Ziliqa is a blockchain network that is using sharding to solve scalability. With the help of this sharding mechanism, Ziliqa can process thousands of transactions per second.

Minimize processing and storage costs: Traditional blockchain design requires each node to store all transactions. As blockchain develops, so does the demand for hardware. But with sharding, each node is only responsible for processing and storing a small portion of the entire network's data, which will reduce the resources required for nodes to participate in the network.

Therefore, the more participants who join as validators, the more decentralized the network will be without incurring high costs. In this way, the problem is alleviated and not only entities with high-end expensive computing resources can actually participate in the process, thus maintaining the democratized nature of the blockchain network.

Improve network performance: Sharding helps improve the overall performance and capacity of the network. In traditional blockchains, the number of nodes participating in the network is increasing day by day, which will increase communication and synchronization between nodes, but performance will decrease.

However, sharding changes this situation. Since each shard can run independently and in parallel, the system can handle more transactions and calculations. New nodes are added only to the shards, not to the entire network, thus increasing the expansion capacity of the network. Efficiency is improved and transactions become smoother, ensuring a better user experience.

Please remember that future developments and improvements in sharding technology may also bring additional advantages, or enhance existing advantages, thereby continuously optimizing the blockchain ecosystem.

What are the limitations of sharding?

Sharding can help blockchain networks become more efficient through many potential benefits, but it also presents a unique set of challenges along the way. Potential vulnerabilities brought by sharding include:

Single shard takeover attack: In a sharded environment, the computing power required to take over a single shard is much lower than the computing power required to take over the entire network. Therefore, a single shard is more susceptible to a "one percent attack" or "shard takeover." It is possible for an attacker with a small number of resources to take over a single shard compared to attacking the entire network.

Cross-shard transactions: Conducting transactions on different shards (cross-shards) will face unique challenges. Cross-shard transactions are complex, and careless management can lead to double-spend issues. During a transaction, if one shard cannot accurately track the status of another shard, users may exploit this vulnerability in an attempt to cause a "double spend problem."

Data availability issues: Sharding makes maintaining the state of the entire network intricate. Because the nodes that maintain certain shards are offline, these shards are unavailable when needed, which can cause data availability issues that disrupt the entire network.

Network Security: Sharding requires the implementation of stable protocols to balance the load between shards. Improper operation may result in uneven data distribution or resource imbalance, which may cause network instability.

Node Synchronization: Node synchronization may cause network delays due to the time it takes to share and update information between different nodes. Additionally, if node processing power slows down or the network connection lags, it may slow down the entire synchronization process, reducing the overall performance of the blockchain network.

Is sharding implemented on Ethereum?

Ethereum has planned sharding implementation as part of the Ethereum 2.0 upgrade. Ethereum 2.0, also known as "Eth2" or "Quiet Phase," is an upgrade to the Ethereum blockchain designed to increase network speed, efficiency, and scalability, thereby increasing the ability to handle more transactions and easing congestion.

As of now, the upgrade is being implemented in phases, with the final phase (Phase 2) including the full implementation of sharding. Ethereum developers hope the upgrade will address challenges faced by the current network, such as scalability and transaction costs.

But it’s worth noting that implementing sharding is inherently challenging, especially maintaining network security and decentralization. Therefore, Ethereum developers have carefully considered and conducted extensive testing of this transition to ensure that the upgrade will be successful once fully implemented.

Conclusion

Overall, sharding represents significant progress in solving the blockchain ternary paradox problem. Sharding brings new complexities and potential shortcomings, but it is expected to improve scalability without affecting decentralization, making the future development of blockchain networks full of endless hope.

This is undoubtedly the reason why many blockchains are exploring sharding as a potential solution. Ethereum is integrating sharding as part of the Ethereum 2.0 upgrade to address scalability issues. Sharding implementation is expected to occur via the Cancun upgrade, a key component of the overall upgrade plan. Still, as with other evolving technologies, the success of a sharding implementation will be determined by factors such as continued research and development and rigorous testing.

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