Abstract
In the year of 2017, more and more datacenters have started to replace traditional SATA and SAS SSDs with NVMe SSDs due to NVMe's outstanding performance [1]. However, for historical reasons, current popular deployments of NVMe in VM-hypervisor-based platforms (such as VMware ESXi [2]) have numbers of intermediate queues along the I/O stack. As a result, performance is bottlenecked by synchronization locks in these queues, cross-VM interference induces I/O latency, and most importantly, up-to-64K-queue capability of NVMe SSDs cannot be fully utilized. In this paper, we developed a hybrid framework of NVMe-based storage system called “H-NVMe”, which provides two VM I/O stack deployment modes “Parallel Queue Mode” and “Direct Access Mode”. The first mode increases parallelism and enables lock-free operations by implementing local lightweight queues in the NVMe driver. The second mode further bypasses the entire I/O stack in the hypervisor layer and allows trusted user applications whose hosting VMDK (Virtual Machine Disk) files are attached with our customized vSphere IOFilters [3] to directly access NVMe SSDs to improve the performance isolation. This suits premium users who have higher priorities and the permission to attach IOFilter to their VMDKs. H-NVMe is implemented on VMware EXSi 6.0.0, and our evaluation results show that the proposed H-NVMe framework can significant improve throughputs and bandwidths compared to the original inbox NVMe solution.