Data Availability
Data Availability
Data availability (DA) is the guarantee that transaction data posted by a rollup sequencer can actually be retrieved by anyone — not just that it was committed to. Without DA, a malicious sequencer could post a state root with hidden data, preventing anyone from computing fraud proofs or reconstructing chain state.
DA is the primary cost driver for rollups. Getting it right is a prerequisite for trust-minimized L2 operation.
Calldata (Pre-Dencun)
Before March 2024, rollups posted transaction data as calldata to Ethereum. Calldata is permanently stored, accessible to smart contracts, and expensive — rollups spent millions per year on it. It was the bottleneck for L2 cost reduction.
EIP-4844 Blobs (Post-Dencun)
The Dencun upgrade (March 13, 2024) introduced blob-carrying transactions. Key properties:
- Blobs are exactly 128 KiB each (4,096 field elements × 32 bytes); Ethereum initially supports ~3/block, targeting 6/block
- Stored by consensus nodes for ~18 days, then pruned — not permanent L1 storage
- Inaccessible from EVM smart contracts (no
BLOBopcode for reading data) - Significantly cheaper than calldata for equivalent data volume (roughly ~$20.56/MB on Ethereum blobs vs. much higher calldata costs)
Most major rollups (Base, OP Mainnet, Arbitrum) migrated to blobs immediately after Dencun.
Limitation: Ethereum blob capacity is still limited. A single high-throughput L2 can fill available blobs, pricing out others.
Celestia
Modular DA network — consensus and data ordering only, no execution or settlement.
- Uses data availability sampling (DAS): light nodes verify availability by downloading random chunks, not full blocks
- Scales throughput by increasing block size without requiring nodes to download everything
- Capacity ~40x greater than Ethereum blobs
- Cost comparison: ~$20.56/MB on Ethereum blobs vs. ~$7.31/MB on Celestia standard vs. ~$0.81/MB via Celestia SuperBlobs — 64–96% cheaper than Ethereum blobs
- ~50% DA market share among rollups using external DA (2025)
- Blobstream bridges DA attestations to Ethereum for rollups that want Celestia DA with Ethereum settlement
EigenDA
Data availability service built on eigenlayer restaking:
- Operators stake ETH via EigenLayer restaking and attest to blob availability
- Security inherits restaked ETH depth (~$18B+ restaked as of 2026)
- EigenDA V1 had a 15 MB/s throughput cap; EigenDA V2 launched on mainnet in July 2025 at 100 MB/s sustained throughput (2,000 MB/s read)
- DAC (Data Availability Committee) architecture — introduces trust assumptions vs. pure on-chain DA
- Native integration with OP Stack chains possible
Choosing a DA Layer
| Layer | Security model | Cost | Capacity | Permanence |
|---|---|---|---|---|
| Ethereum calldata | Ethereum validators | High | Low | Permanent |
| Ethereum blobs | Ethereum validators | Medium | Moderate | 18 days |
| Celestia | TIA stakers + DAS | Low | High | Pruned |
| EigenDA | Restaked ETH | Low-medium | Very high | Pruned |
Most new OP Stack chains targeting high throughput are choosing Celestia or EigenDA over Ethereum blobs.
Related
rollups · eigenlayer · op-stack · ethereum-l2s