HP-Mapper: A High Performance Storage Driver for Docker Containers

Docker containers are widely deployed to provide lightweight virtualization, and they have many desirable features such as ease of deployment and near bare-metal performance. However, both the performance and cache efficiency of containers are still limited by their storage drivers due to the coarse-grained copy-on-write operations, and the large amount of redundancy in both I/O requests and page cache. To improve I/O performance and cache efficiency of containers, we develop HP-Mapper, a high performance storage driver for Docker containers. HP-Mapper provides a two-level mapping strategy to support fine-grained copy-on-write with low overhead, and an efficient interception method to reduce redundant I/Os. Furthermore, it uses a novel cache management mechanism to reduce duplicate cached data. Experiment results with our prototype system show that HP-Mapper significantly reduces copy-on-write latency due to its finer-grained copy-on-write scheme. Moreover, HP-Mapper can also reduce 65.4% cache usage on average due to elimination of duplicated data. As a result, HP-Mapper improves the throughput of real-world workloads by up to 39.4%, and improves the startup speed of containers by 2.0x.