I. Introduction
Recent years have witnessed phenomenal successes of cloud storage in hosting data with the economies of scale. Specifically, today’s cloud storage infrastructures have provided a spectrum of services exemplified by Amazon S3 (Simple Storage Service), EBS (Elastic Block Storage), EFS (Elastic File System), Glacier (Archive Storage), and so forth. As the most basic data-organization form and the most user-friendly information carrier, files are typically hosted by two types of cloud storage services with distinct design principles at the moment: object storage (e.g., Amazon S3, OpenStack Swift and Aliyun OSS [1]) and filesystem storage (e.g., Amazon EFS, Azure File Storage and Aliyun NAS [2]).