UniDrive: Synergize Multiple Consumer Cloud Storage Services

Consumer cloud storage (CCS) services have become popular among users for storing and synchronizing files via apps installed on their devices. A single CCS, however, has intrinsic limitations on networking performance, service reliability, and data security. To overcome these limitations, we present UniDrive, a CCS app that synergizes multiple CCSs (multi-cloud) by using only few simple public RESTful Web APIs. UniDrive follows a server-less, diem-centric design, in which synchronization logic is purely implemented at client devices and all communication is conveyed through file upload and download operations. Strong consistency of the meta data is guaranteed via a quorum-based distributed mutual-exclusive lock mechanism. UniDrive improves reliability and security by judiciously distributing erasure coded files across multiple CCSs. To boost networking performance, UniDrive leverages all available clouds to maximize parallel transfer opportunities, but the key insight behind is the concept of data block over-provisioning, and dynamic scheduling. This suite of techniques masks the diversified and varying network conditions of the underlying clouds, and exploits more the faster clouds via a simple yet effective in channel probing scheme. Extensive experimental results on the global Amazon EC2 platform and a real-world trial by 272 users confirmed significantly superior and consistent sync performance of UniDrive over any single CCS.