Drivechains are decentralized storage
In Everscale, in addition to the usual workchains for data processing, there is a type of chain called a drivechain. Drivechains are decentralized storage device in the Everscale network. At its core, a drivechain is a workchain that is optimized in order to store large amounts of data.
Drivechains have special smart contracts located on them. In order to store a file on a drivechain, you need to deploy a “file index” smart contract (similar to the index used on the Unix or Linux operating systems). This “file index” contains certain information that allows you to store and extract files, as well as pay for that storage.
How does it work?
Since drivechains are related to decentralized data storage, everything starts with a dedicated, scalable number of validators that store the associated data. Validators are selected using the D’Elector smart contract. A validator commits to providing space of a certain size meeting the system’s requirements on their disk and commits to transferring this data, which they receive as a result of synchronization, within a certain period of time. If an applicant does not meet any of these system requirements, they cannot become a validator.
The whole business of decentralization is essentially an economic game. Therefore, in order to make sure that validators actually fulfill the stated conditions, that is, storing data, due to the option of the simplest possible algorithm — random sampling, small blocks of information are deterministically queried. This produces a scenario where everyone checks everyone else according to a deterministic algorithm.
In addition, to make sure that validators take up disk space, files consisting of quasi-random bits that fill the entire storage space are written there. When there is an actual storage request, these random files are replaced by the necessary (client) files.
Checking information storage and random sampling are an essential part of the process, but they are not sufficient to make sure that the system is operating correctly. Everscale has thus gone further and also decided to perform a data transfer check with final acknowledgement of receipt from the client, since data transfer is currently the most expensive procedure in this chain.
If a validator is out of sync for any reason, they must notify the drivechain D’Elector contract. If more than 10% of the validators are out of sync, the D’Elector must start adding new validators to the DeDrive. This results in slow rotation, but it is enough to pass information between validators.
If it happens that files are not available, are damaged, or are not being transferred, when a certain number of such situations occur, the validator’s stake is reduced and they are eventually subjected to slashing. In this way, a system is built up where nobody has a vested interest in not storing, not transferring, or lying about the data.
What are the use-cases?
In fact, anybody can store anything on drivechains. The data will be stored in an encrypted format, and not one validator will be able to decrypt the data and read it. An example of a perfect fit for storage on drivechain is media storage for NFTs. Also, some of the first consumers of drivechains will be other workchains that are archiving old states.
The pricing policy for this kind of decentralized storage will be formed closer to the service’s market launch, and it promises to be balanced and competitive so that it will be interesting for validators, users, and projects to get involved. The launch is due to take place in a couple of months.
