Improving Copy-On-Write Performance in Container Storage Driver

Authors: Kevin Xu, and Randy Shain, EMC Corporation
Copy-On-Write (COW) is widely used in file system, storage and container such as via DevMapper, AUFS etc. However, in practice, COW is usually complained due to its performance penalty e.g,: lookup overhead, disk IO amplification and memory amplification (duplicate copies). In this presentation, we share our inspiring solution to effectively mitigate those long standing performance issues specially for dense container environment.

Our solution, namely, the Data Relationship and Reference (DRR), is a lightweight and intelligent software acceleration layer atop of existing COW framework that can speed up cross-layer lookup, reduce duplicated disk IO and potentially enable the possibility of single data copy in memory. We present our design and prototype based on DevMapper for Docker and demonstrate such approach’s promising performance gains in launch storm and App data load use cases.

Learning Objectives

Dense Docker use case: challenge and opportunity
COW essential and performance insight
New approach DRR atop existing COW: why and how
Design and prototyping with DM-thin
Outlook more opportunities