Under the hood: Facebook’s cold storage system

What this post added

This post details the development of Meta's cold storage system, a new capability focused on efficiently and durably storing less frequently accessed photos. It describes the full-stack approach, including custom data center design, low-power servers based on Open Vault specifications with modified drive power management, and optimized rack configurations. The software design emphasizes durability, with principles like eliminating single points of failure and self-describing data. Key technical innovations include the use of Reed-Solomon erasure coding for data redundancy and an 'anti-entropy' background process for detecting and correcting 'bit rot'. The system is designed to scale and improve with capacity additions through data rebalancing.