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Separate data availability from permanent storage
Useful first : Layer 2 rollups explained · Ethereum gas and EIP-1559
Challenge the system · Step 4 / 6
Blobs provide a dedicated mechanism for publishing data associated with Ethereum transactions, particularly useful to rollups.
The essentials
Blobs provide a dedicated mechanism for publishing data associated with Ethereum transactions, particularly useful to rollups. Their fee market is distinct from ordinary execution gas. They help separate the demand to publish data from the demand to execute EVM instructions.
How it works
The EVM does not read arbitrary blob contents as ordinary contract storage. Commitments allow the data to be related to the transaction, while availability and retention follow protocol rules. Rollups need the relevant data to reconstruct and verify their state. Data availability is different from a proof that execution was correct.
What to watch
Do not assume a blob is permanent archival storage or a free way to store a website. Historical reconstruction may rely on archival infrastructure beyond the protocol’s required retention. For a Layer 2 assessment, ask where transaction data is published, who can retrieve it and what users need to exit if the operator disappears.
Understand the details
Blob transactions provide a dedicated data path used by rollups. The execution environment refers to commitments rather than treating the blob payload as ordinary contract-readable storage. This separates data publication economics from ordinary execution gas, although user-facing rollup fees can combine several components.
Boundaries and common mistakes
Availability during the protocol’s required window is not a promise of permanent archival access. Rollups and other services may need their own long-term storage strategy. Parameters evolve with upgrades, so distinguish the architectural role from current capacity or retention numbers. A hash commitment proves a relationship to data, not that a convenient archive will always serve it.
The mechanism at a glance
- 01Rollup data
- 02Blob publication
- 03Commitment and availability
- 04Separate long-term archive
Read these as connected concepts, not necessarily consecutive steps.
Read the explanation
Blob transactions provide a dedicated data path used by rollups. The execution environment refers to commitments rather than treating the blob payload as ordinary contract-readable storage. This separates data publication economics from ordinary execution gas, although user-facing rollup fees can combine several components.
Put the mechanism into context
A researcher wants to reconstruct historical rollup activity long after publication. Draw the path from a blob commitment to the actual data and then to replayable state. Identify the extra archive dependency instead of assuming every ordinary node retains everything forever.
Apply it in the workshop →What this mechanism does not guarantee
Availability during the protocol’s required window is not a promise of permanent archival access. Rollups and other services may need their own long-term storage strategy. Parameters evolve with upgrades, so distinguish the architectural role from current capacity or retention numbers. A hash commitment proves a relationship to data, not that a convenient archive will always serve it.
The distinction that changes the analysis
A data-availability mechanism and an archive service solve different problems. Before relying on historical reconstruction, identify who retains the required data and for how long. A commitment to data does not provide an unlimited archive of its contents.
Explain it yourself
Revisit the case above. Name what is established, what remains to be checked and the evidence needed to conclude. A strong answer addresses both sides of the diagram.
Apply the lesson to a case
A researcher wants to reconstruct historical rollup activity long after publication. Draw the path from a blob commitment to the actual data and then to replayable state. Identify the extra archive dependency instead of assuming every ordinary node retains everything forever.
It can verify matching data when available, but it does not reveal the full payload. Reconstruction also needs the data and the relevant execution rules. Specify archive availability and integrity checks separately; they solve different problems.
Inside a Layer 2 rollup
Transaction
The user signs on the selected Layer 2, which has its own chain identifier.
Terms in this lesson
- Rollup
- A scaling system that links off-chain execution to a base layer using published information and a proof or challenge mechanism.
- Gas
- A measure of execution resources; gas units and the price per unit are separate quantities.
Prepare a correction note
Describe the passage and the proposed correction. This creates a local note for you to share; it sends nothing. Do not include personal or confidential information.