Understanding and Surpassing Dropbox: Efficient Incremental Synchronization in Cloud Storage Services

Cloud storage services allow files to be synchronized among multiple users or devices easily. To minimize the amount of network traffic, these services utilize incremental data synchronization techniques. However, little is known about their particular mechanisms and corresponding efficiency. In this paper, we focus on Dropbox, the most popular cloud storage service, as a case study. We examine the bandwidth consumption on the Dropbox client under typical synchronization scenarios, and find that Dropbox wastes a lot of traffic due to matching unrelated chunks to compute incremental changes. More seriously, when file conflicts among clients, Dropbox directly downloads the whole file instead of the incremental changes. To solve these problems, we design and implement an efficient incremental synchronization system named Minbox. MinBox employs an efficient locality-sensitive hash for better similar chunk matching. Moreover, Minbox could forward the incremental changes during confliction by maintaining the relation of conflicting files. In comparison with Dropbox, Minbox significantly reduces network traffic and resolves file conflict with little overhead.