KoinlyticsA rollup is only trust-minimized if anyone can reconstruct its state. That requires the transaction data to be published somewhere everyone can access, cheaply and verifiably. That "somewhere" is the data availability layer, and until 2024 it was Ethereum L1. That is expensive.
Why DA is a separate concern
A rollup does two things: execute transactions (compute) and publish data (bytes). Compute can be arbitrary and complex; data must just be reliably available. Rollups were paying Ethereum's execution price for storage bytes that never needed to be executed on L1. Cost mismatch.
The three answers
- Ethereum blobs (EIP-4844). Since March 2024. Ethereum L1 offers a purpose-built blob space with its own fee market. Cheaper than calldata by 10-100x.
- Celestia. A chain purpose-built for DA. Cheaper than Ethereum blobs. Sovereign rollups (Manta, Movement) post here.
- EigenDA. Built on EigenLayer restaking. Uses re-staked ETH validators for security. Sits somewhere between the two on cost.
Cost comparison
Rough numbers for posting 1 MB of data:
- Ethereum calldata (pre-Dencun): $50-500 depending on gas.
- Ethereum blobs (post-Dencun): $0.05-0.5.
- Celestia: $0.01-0.05.
- EigenDA: comparable to Celestia.
Security trade-offs
Ethereum blobs inherit Ethereum's full security. Celestia has its own validator set (~100 validators, tens of millions in stake). EigenDA depends on restaked ETH and the AVS slashing conditions. For a rollup that wants Ethereum settlement, using non-Ethereum DA means "validium" trust: settlement is on L1 but data lives elsewhere and requires the DA layer's honesty.
Danksharding is the endgame
Ethereum's plan is to eventually offer massive amounts of blob space (called Danksharding). If that ships, external DA layers may lose their cost edge. Meanwhile, they matter because they exist now.