# DA Layer The DA Layer entails making the transaction and state data available. Nova chooses the **Validium mode** for storing data. Under classic Rollup mode, the majority of Ethereum gas costs go to Data Availability, and not proof verification. This is because it is very gas-intensive to store data on Ethereum. In Validium mode, Nova's data is stored off-chain with a Data Availability Committee (DAC). This Data Availability Committee oversees the correct state update as well as keep a copy of the data that was processed. In the very near future, Nova will integrate with external DA solutions, for example, Celestia, EigenDA, Avail, etc., so that data will be stored in a more decentralized approach with censorship resistence. --- # 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.zklink.io/architecture/da-layer.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.