Introduction to DACS ~A Flexible Decentralized Storage Bestowing Data Across Generations

Introduction

Xenea has established a unique architecture that integrates Layer 1 and decentralized storage. In this system with decentralized storage, we must address the critical issue of "data continuity".

In blockchain alone, handling lightweight and structured data such as account states or transaction histories doesn't significantly challenge data continuity. Nodes storing these data are easy to join, and with sufficient copies decentralized worldwide, the risk of data loss is extremely low.

However, when handling large-volume data like images and videos in decentralized storage, ensuring continuity becomes a major challenge. These data can range from several MB to GB and may need to be stored for extended periods. Moreover, if such data is handled as NFTs and the data itself holds value, it might need to be preserved across generations, spanning years or even decades.

Realistically, all recording media have physical lifespans. Therefore, decentralized storage requires a mechanism to sustainably store data itself to overcome the limitations of recording media. DACS (Decentralized Autonomous Contents Storage) was developed for this purpose.

This article introduces the characteristics and advantages of DACS based on existing blockchain-based decentralized storage solutions.

Existing Blockchain-Based Decentralized Storage

Characteristics of IPFS/Filecoin

IPFS (InterPlanetary File System) is a hash-based decentralized file system. Unlike traditional centralized HTTP, it aims to create a decentralized web by leveraging P2P networks.

IPFS uses a mechanism that identifies files through unique hash values generated based on file contents, making it primarily suitable for static file storage.

In IPFS, users can retrieve content from nearby nodes when accessing files, enabling fast data transfer and efficient bandwidth usage. Additionally, with the same file stored across multiple nodes, there are no single points of failure, ensuring high availability and fault tolerance.

However, IPFS itself is merely a file system and does not inherently guarantee data continuity. For instance, if a specific company hosts IPFS storage, data might be lost due to the company's circumstances. If NFT data is stored in such a service, there's a risk of becoming inaccessible if the storage provider or NFT issuer terminates their service.

Filecoin functions as the incentive layer for IPFS using the cryptocurrency $FIL. Users store data by establishing storage deals with storage miners. This means data is not stored across the entire Filecoin network but on specific miners' storage nodes. Consequently, data continuity depends on miners, and data can be lost upon contract termination or miner withdrawal. In essence, Filecoin can be viewed as a storage marketplace.

Characteristics of Arweave

Arweave is a decentralized storage network designed to store data permanently. Unlike Filecoin, once data is stored, it is copied between miners and maintained across the entire network. This ensures data is semi-permanently stored and cannot be tampered with or deleted. Users pay a one-time storage fee in $AR tokens, which might seem more expensive compared to other storage services, but guarantees perpetual storage.

Challenges with Existing Decentralized Storage

Looking at IPFS/Filecoin and Arweave as examples of existing decentralized storage:

IPFS is a file system without an inherent mechanism to guarantee data continuity. Filecoin, its incentive layer, depends on miners for data continuity. Arweave, while storing data semi-permanently across the network without individual miner contracts, requires users to pay premium fees. Both are also premised on handling static files.

DACS aims to overcome these challenges, enabling data continuity and handling dynamic data to realize a more flexible decentralized storage system.

DACS: Xenea Blockchain's Decentralized Storage

DACS Overview

The decentralized storage function in the Xenea Blockchain is provided by DACS (Decentralized Autonomous Contents Storage). This architecture is based on a peer-reviewed IEEE paper, "Sustainable NFT Blockchain Storage for High Availability and Security".

DACS enables a more flexible system that guarantees data continuity and addresses dynamic data, which is difficult with traditional blockchain-based decentralized storage. This is possible because DACS can integrate the Xenea Blockchain with multiple file systems.

A common misunderstanding is that DACS itself is a file system. DACS is an architecture for integrating the Xenea Blockchain with file systems, with actual data storage handled by hosted file systems.

File systems integrable with DACS include IPFS, known as a hash-based file system, and a proprietary file system we are developing (as of December 2024) that supports dynamic data. By combining with SGM (Sustainable Generation Manager) and FASTD (FAST Track Contents Delivery Manager), DACS ensures data continuity and caching capabilities.

In the initial stages of the Xenea Blockchain launch, DACS will only support IPFS. To ensure network stability and a comfortable user experience, DACS node participation will be permission-based during this phase.

Sustainable Generation Manager: SGM

SGM is a technology for perpetually maintaining data on a decentralized storage network. This system automatically migrates data to storage devices of other DACS nodes before the physical lifespan of storage devices is reached, creating an environment where data can be inherited across generations.

To ensure data continuity, SGM monitors and manages timestamps for each storage. When a storage's validity period expires, it replicates data to DACS nodes with the closest network distance. Once replication is complete, the data on the original DACS node is deleted, and the space becomes available for new use.

Data replication from the first generation to the second generation DACS is performed in the process shown in the flow diagram below. Note the expiration date of the data which triggers the replication can be set from 1 to 365 days, with the default value set to 180 days.

FAST Track Contents Delivery Manager: FASTD

In certain cases, specific data may require low-latency access depending on its purpose. To address such needs, FASTD (FAST Track Contents Delivery Manager) manages content in the cache area of DACS nodes, enabling low-latency data access. Content organizers can designate data requiring low-latency access as FAST track.

Conclusion

In this article, we focused on the challenge of data continuity, introducing the characteristics of existing blockchain-based decentralized storage solutions and DACS developed by Xenea. While existing solutions like IPFS/Filecoin and Arweave have their own excellent features, they have limitations in data continuity and handling dynamic data.

Against this background, the DACS provided by Xenea, based on a peer-reviewed IEEE paper, proposes a new framework that transcends these limitations. By integrating blockchain with multiple file systems, DACS achieves a more flexible decentralized storage. Particularly, the mechanism of data inheritance across generations through SGM offers a solution to the fundamental challenge of physical storage device lifespans. Moreover, with FASTD implementation, it becomes possible to appropriately handle data requiring low-latency access.

These characteristics of DACS are expected to significantly contribute to long-term storage of digital assets including NFTs and continuous maintenance of various types of data.