Explanation of the Important Upgrade EIP-4844

The EIP-4844 upgrade introduces a new transaction type called BlobTx and a new storage space called Blob. This storage space resides in the Ethereum Consensus Layer, making it inaccessible to the Execution Layer's EVM. Consequently, data stored in this location cannot be accessed by smart contracts.

As a decentralized ledger, storage has always been a significant topic for blockchain. If the storage capacity of each block is too small, it can lead to reduced transaction capacity and quantity. The pressure of competition can cause an increase in gas fees and render the blockchain unusable. On the other hand, if the storage capacity of each block is too large, it will increase the pressure on nodes, requiring each node to improve the quality of its hardware, thus reducing the security of the decentralized network due to fewer running nodes.

This upgrade introduces blob storage, where each blob will have up to 128KB of space to store additional information. Each Ethereum block will support a maximum of 6 blobs, totaling a maximum of 768KB. This means that each Ethereum block can be expanded by up to approximately 0.7MB. Calculating based on an Ethereum block every 12 seconds, with each block defaulting to supporting 3 blobs, there will be approximately 21,600 blobs per day, resulting in nodes adding around 2.6 GB of data. Therefore, blobs are designed with a lifespan of approximately 18 days (4096 epochs) based on their use cases, after which nodes will delete them. Consequently, storing data in blobs incurs very low gas fees.

Compare the differences between the following types of storage

Unable to be read and utilized by smart contracts on the EVM, and also subject to deletion after a period of time, what's the use of Blob? Currently, Layer 2 benefits the most from it.

Let's take a look at how Layer 2 works

Taking Optimistic Rollup as an example, transactions that occur on Layer 2 are captured by the Layer 2 Sequencer and merged and compressed (Rollup) into more compact data, typically including the state root, compressed transaction data, proof information, etc., and then uploaded to the Ethereum mainnet. This information is not parsed or read by Ethereum or smart contracts, but is mainly used to ensure the security of L2 data, prove the authenticity and reliability of its transactions, and recover some states in emergencies.

For example, in Optimistic Rollup, operations such as withdrawing funds require a waiting period of 7 days. During this time, validators verify the relevant data to discover if the Sequencer has engaged in any malicious behavior. After the seven-day challenge period, the transaction can be deemed secure and confirmed. Currently, this information is stored on the Ethereum mainnet in the form of Calldata, which provides the most secure and reliable storage but requires a relatively high Gas fee. Since Ethereum's block capacity is limited, this also restricts the scalability and development of L2. However, blobs can alleviate this issue. L2 can strip the relevant data used for verification and store it in blobs because they do not need to be permanently stored; they only need to be accessible during the challenge period. Therefore, this can greatly reduce Gas fees.

Below is a flowchart and comparison of the process before and after the upgrade: