Vitalik Buterin says The Purge can help reduce Ethereum’s complexity and storage requirements

One of the problems of Ethereum, or any blockchain, is that it grows in size over time. This means an increase in the complexity of its code and its storage requirements.

A blockchain must retain all the data throughout its history which needs to be stored by all clients and downloaded by new clients. This leads to a constant increase in client load and sync time.

Moreover, code complexity increases over time because it is “easier to add a new feature than to remove an old one,” Vitalik Buterin wrote on his blog.

Therefore, Buterin believes that developers have to actively work towards stemming these growing trends while preserving Ethereum’s permanence. Buterin has therefore presented The Purge—a plan with three parts that aim to simplify the blockchain and reduce its data load.

Part 1: History expiry

A fully-synced Ethereum node currently requires around 1.1 TB of storage space for the execution client. It requires a few hundred more gigabytes for the consensus client. According to Buterin, most of this data is history, such as data about historical blocks, transactions, and receipts, many of which are several years old. To store all this history, the disk space required keeps increasing by hundreds of gigabytes every year.

Buterin believes that the problem can be solved by something called History Expiry.

Each block on a blockchain points to the previous one via a hash link. This means that consensus on the current block indicates consensus on history.

According to Buterin, as long as the network has consensus on the current block, any related historical data can be provided by a single actor through a Merkle proof, which allows anyone to verify its integrity. This means that instead of having every node store all the data, each node could store a small percentage of the data, reducing storage requirements.

Buterin basically suggests adopting the operating model of torrent networks, where each participant stores and distributes only a small part of the data…