Overview

When Filecoin Storage Providers accept FIL+ Storage deals, there is a agreement to make all the data available for “fast retrieval”. This means as well as storing the sealed copy of the data, another “hot copy” of the data must be stored so that it can be retrieved without having to unseal the sealed copy.

However, this agreement to make a hot copy available is not guaranteed by the core Filecoin protocol. Spark aims to solve this.

Spark is a trustless protocol for sampling retrievals from Filecoin Storage Providers. Spark checkers (or workers) make retrieval requests to Filecoin Storage Providers and report on the responses. Spark checkers are then rewarded for their contribution to Spark on a regular basis.

The data collected by Spark checkers can then be fed into reputation systems or even back on chain to incentivise Storage Providers to store a hot copy and serve it to requesting clients in a performant and reliable way.

Spark Protocol Steps

At a high level, the Spark protocol is split into the following steps. More information is given in the pages dedicated to each step.

1. Committee Building: The online Spark checkers are clustered into several committees. The checkers in each committee are given the same tasks.
2. CID Sampling: Each committee is given a random (CID, Storage Provider) pair to test.
3. Retrieval with Attestation: Spark checkers retrieve CID content from Storage Providers and obtain the attestation token with the payload.
4. Proof of Data Possession: Spark checkers create a proof that the entire CID content was retrieved.
5. Measurement: Spark checkers report each job outcome to Spark’s on-chain Impact Evaluator, built using the Meridian framework
6. Evaluation & Verification: The Spark smart contract verifies the measurements and evaluates the contribution of each Spark checker.
7. Reward: The smart contract rewards each Spark checker based on their contribution to Spark in the latest round.

For a deeper dive into the Spark protocol and its latest developments, please head here.

On this page

• Overview
• Spark Protocol Steps