DAVM Distributed Asynchronous Data Versioning Mechanism for Replicas

We present a distributed and asynchronous versioning mechanism (DAVM) in this paper to identify consistent replicas for each encoding block in BW-RAID, which uses "mirroring and RAID4" encoding scheme to improve the system performance and disk space utilization. DAVM has three advantages: Firstly, it is distributed and asynchronous in management. Secondly, it is correct and workable in any running status of the storage system, including normal status, recovery status. Thirdly, it is independent of standard storage protocols. On the basis of DAVM, we implement an asynchronous and low overhead BW-RAID scheme. Experiments show that DAVM can identify consistent replicas for all logical blocks normal state and recovery states. In sequential write tests, compared to synchronous scheme, our asynchronous scheme improves the average bandwidth by 25.58% in average, and improves the system throughput stability by 25.10% in average, with the storage overhead less than 0.5%. In real workloads replays, our scheme improves the average IOPS by 42.23% in average and reduces the average write latency by 31.76% in average.