Sion: Elastic Serverless Cloud Storage

Cloud object storage such as AWS S3 is cost-effective and highly elastic but relatively slow, while high-performance cloud storage such as AWS ElastiCache is expensive and provides limited elasticity. We present a new cloud storage service called ServerlessMemory, which stores data using the memory of serverless functions. ServerlessMemory employs a time-window-based data placement strategy to effectively segregate old and new data and provides high elasticity, performance, and a pay-per-access cost model with extremely low cost for a new memory-based storage. We then design and implement SION (Serverless I/O Nirvana), a persistent and elastic cloud storage system, which seamlessly couples the function-based ServerlessMemory layer with a persistent, inexpensive cloud object store layer. SION enables durability despite function failures using a fast parallel recovery scheme built on the auto-scaling functionality of a FaaS (Function-as-a-Service) platform. We evaluate SION extensively using three real-world applications and results show that SION achieves 27.77% and 97.30% tenant-side cost reduction compared to InfiniCache (a serverless-function-based object cache) and AWS ElastiCache respectively, while offering pay-per-access with competitive performance.