EFLOG: A Full Stream-Logging Scheme with Erasure Coding in Cloud Storage Systems

Abstract

Large-scale cloud storage systems use the logging mechanism to sequentially write data in an append-only manner. The write stream needs to be first appended and persisted into logging files, and then encoded with erasure coding (EC) in underlying storage. This introduces significant overhead to small write operations. To solve this problem, we propose EFLOG, a full-streaming storage framework that combines Logging and inter-log EC mechanisms. EFLOG evenly schedules front-end write streams across log files in each disk with append-only manner. In background, EFLOG determines unprotected logged data and seals them into ECblocks. Afterwards, EFLOG concurrently encodes data with multi-threads and stores parity data into parity disks. Results of our trace-driven evaluation show that, EFLOG can achieve up to 1.01GB/s write throughput with RS(4, 2) codes built upon 6 SSD disks.