VFRM: Flash Resource Manager in VMware ESX Server

One popular approach of leveraging Flash technology in the virtual machine environment today is using it as a secondary-level host-side cache. Although this approach delivers I/O acceleration for a single VM workload, it might not be able to fully exploit the outstanding performance of Flash and justify the high cost-per-GB of Flash resources. In this paper, we present the design for VMware Flash Resource Manager (VFRM), which aims to maximize the utilization of Flash resources with minimal CPU, memory and I/O cost for managing and operating Flash. It borrows the ideas of heating and cooling from thermodynamics to identify the data blocks that benefit most from being put on Flash, and lazily and asynchronously migrates the data blocks between Flash and spinning disks. Experimental evaluation of the prototype shows that VFRM achieves better cost-effectiveness than traditional caching solutions, and costs orders of magnitude less memory and I/O bandwidth.