Persistent memory (PMEM) is a type of non-volatile DRAM (NVDIMM) that has the speed of DRAM but retains contents through power cycles. It is a new layer that sits between NAND flash and DRAM, providing faster performance. It’s also non-volatile unlink DRAM.

vSphere 6.7 supports two modes of accessing persistent memory:

  • vPMEMDisk – presents NVDIMM capacity as a host local datastore which requires no guest operating system changes to leverage this technology
  • vPMEM – exposes NVDIMM capacity to the virtual machine through a new virtual NVDIMM device. Guest operating systems use it directly as a block device or in DAX mode.

The following chart shows the result of a performance test run using the MySQL benchmark of Sysbench. The benchmark measures the throughput and latency of a MySQL workload. Here, we ran the tests with 3 tables, 9 threads, and an 80-20 read-write ratio. We ran the MySQL server in a VM hosted on vSphere 6.7.  

The blue bars show throughput measured in transactions per second. The green line shows latency, measured as the 95th percentile in milliseconds. 

We observe that virtual PMEM can improve performance by up to 1.8x better throughput and 2.3x better latency over standard SSD technology.
 

Virtual PMEM can improve performance by up to 1.8x better throughput and 2.3x better latency over standard SSD technology

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