# Ethereum long term DA The introduction of blobs in the [Dencun](https://blog.ethereum.org/2024/02/27/dencun-mainnet-announcement) hard fork has allowed L2s to post their transaction data using “data blobs”, significantly [reducing gas fees.](https://medium.com/hemera-protocol/post-eip-4844-the-primary-factors-impacting-gas-fees-on-layer-2-blockchains-df64799d28ec) However, blobs are only stored by Ethereum nodes for \~18 days before being expired and deleted to save on data storage costs. Yet, while blobs are not needed to reconstruct Ethereum mainnet transactions, they are necessary for each L2 to reconstruct their own history (e.g. for verification purposes). Any L2s using the Ethereum mainnet as their [Data Availability layer](https://l2beat.com/scaling/data-availability) need transaction data to be available when a new full node is set up and joins the L2 network without P2P sync. Existing L2s mainly sync transaction history from the L2 network itself, which has centralization risks (e.g. in the rare case that peer nodes are corrupted and transaction history is lost). Thus, the Ethereum ecosystem needs an alternative form of blob preservation to ensure L2s have access to blob data whenever needed, in turn keeping the Data Availability guarantee. As discussed in [Paradigm’s recent blog](https://www.paradigm.xyz/2024/05/how-to-raise-the-gas-limit-2) , a robust blob storage infrastructure will also apply to L1 history data storage, providing a viable solution to the question raised by [EIP-4444](https://eips.ethereum.org/EIPS/eip-4444) in the future. Since Hemera Network continously indexes and stores on-chain data, including calldata & blobs, providing a BlobArchive service is a natural use case. **Checkout our blog here for more details:** --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.thehemera.com/welcome/account-centric-indexing-protocol/example-hemera-use-cases/ethereum-long-term-da.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.