Improving Spatial Locality in Virtual Machine for Flash Storage

Flash-based solid-state drives (SSD) are being widely adopted in virtualized environments to improve the I/O performance due to their low latency and high throughput compared with existing hard disk drives. In the virtualized environment, the performance of SSDs fluctuates significantly according to the I/O patterns from the virtual machine. For example, random writes have a significantly negative impact on the performance of SSDs compared with sequential writes due to the characteristics of SSDs. In this paper, we propose an address reshaping technique for SSDs in the virtualization layer to improve the spatial locality and the performance of random writes. Our scheme transforms random write requests into sequential write requests in the virtualization layer and thus enables the virtualization layer to issue the transformed sequential requests to SSDs. The experimental results show that the optimized scheme improves the performance by up to 97% compared with the existing scheme under random write workloads.