RHOBBS: An Enhanced Hybrid Storage Providing Block Storage for Virtual Machines

Non-volatile memory devices such as Solid State Drives (SSDs) are becoming more popular due to their high performance, increasing capacity and decreasing cost in recent days. However, it is unfeasible to store all data in SSDs because it is too expensive compared with Hard Disk Drives (HDDs). Hybrid storage system may represent a balanced solution between high performance and acceptable cost. This paper presents a hybrid storage system called RHOBBS, which provides a hybrid block device storage for virtual machines. RHOBBS is based on Ceph and uses Object Storage Nodes (OSDs) for storing objects. It groups OSDs into two logical storage pools, the high performance pool (SSD pool) and mass volume pool (HDD pool). RHOBBS strips VM disk image into objects and storing them in different storage pools according to their contents. RHOBBS then shuffles objects across different storage pools according to their accessing patterns periodically as well. We perform an evaluation of RHOBBS and the experiments show that RHOBBS achieves significant performance improvement than original Ceph and our previous study.