ACOS: Apple's Geo-Distributed Object Store at Exabyte Scale

Over the last two decades, with the advent of mobile computing and Internet streaming, Apple has expanded its user base and services significantly. With this growth, we have seen an increased volume and diversity of data storage, ranging from backups, personal photos and videos, to music libraries, TV shows, and live streaming. In this paper, we present ACOS, Apple's object store designed to meet the specific requirements of user-facing and internal services, by accommodating a wide range of content and access patterns. ACOS has been in production for over a decade, storing several exabytes of objects and serving billions of requests per day. With its georeplicated architecture using both local and regional replication mechanisms, ACOS is cost-efficient and highly scalable, available, and durable. The evaluation of our production deployment shows its throughput and latency performance as well as its resilience to hardware and data center failures. This paper presents the design and evolution of ACOS, evaluates its performance in production, and demonstrates its capacity to scale and support Apple's current storage needs and future growth.