ThinStore: Out-of-Band Virtualization with Thin Provisioning

Traditional storage virtualization systems are faced with the problem of poor storage utilizations, leading to expensive capital expenditures and high energy consumptions. To address this issue, we design and implement Thin Store, an out-of-band virtualization system that supports thin provisioning of storage resources. Thin Store automatically allocates storage capacity only when new data is written and employs the probing reclamation policy to reclaim unused storage space. To improve the system performance, we introduce the mapping metadata caching and lazy update mechanisms to reduce the interaction overhead between the metadata server and clients. The experimental results demonstrated that Thin Store significantly improved the storage utilization with acceptable performance overhead. For example, it delivered approximately 88.7% storage space savings when file system utilization was 10%. We also examined the effectiveness of our reclamation policy. It reclaimed 83.6% of unused storage resources for a large file workload. In addition, various file systems showed different friendliness with our system. Compared with ext 3, ext 4 reduced the storage space overhead by 10.6% in a small file workload.