Performance Study on PMEM in vSphere

Persistent Memory (PMEM) is modern technology that provides us with a new storage tier that will be beneficial for Enterprise Applications that need reduced latency and flexible data access. Examples are (in-memory) database platforms for log acceleration by caching, data writes and reduced recovery times. High Performance Computing (HPC) workloads can also greatly benefit from PMEM for example using it for in-memory check-pointing.

PMEM converges memory and storage. We now have the possibility to store data at unprecedented speed as PMEM its average latency is less than 0.5 microseconds. PMEM is persistent, like storage. That means that it holds its content through power cycles. The beauty of PMEM is that it has characteristics like typical DDR memory; It is byte-addressable allowing for random access to data. Applications can access PMEM directly for load and store instructions without the need to communicate with the storage stack.

 
vPMEMDisk: vSphere presents PMEM as a regular disk attached to the VM. No guest OS or application change is needed to leverage this mode. For example, legacy applications on legacy OSes can utilize this mode.  Note that vPMEMDisk configuration is available only in vSphere and not in bare-metal OS. 2.vPMEM: vSpherepresentsPMEM as a NVDIMM device to the VM. Most of the latest operating systems (for example, Windows Server 2016 and CentOS 7.4) support NVDIMM devices and can expose them to the applications as block or byte-addressable devices. Applications can use vPMEM as a regular storage device by going through the thin layer of the direct-access (DAX) file system or by mapping a region from the device and accessing it directly in a byte-addressable manner. This mode can be used by legacy or newer applications running on newer OSes.

Persistent Memory Performance on vSphere 6.7: Performance Study |  27v. vMotionPerformancevSphere supports vMotion of both vPMEMDisk and vPMEM. vPMEMDisk vMotion is conducted as XvMotion, where both local storage and memory contents are transferred to another host. vPMEM vMotion is conducted as compute vMotion, where vPMEM is transferred as memory along with vRAM. Note that, PMEM is a host local storage and seamless live-migration like vMotion is only possible in vSphere environment (unlike bare-metal OS) We used 2 identical hosts connected over 40 GbE network. We created 3 vmknics for vMotion over the 40 GbE physical NIC.

 

I will share the update information shortly. I hope this has been informative and thank you for reading!