In facing the exponential data growth globally, a major memory issue emerges. DRAM is not scaling along with data center memory needs, as the following figure illustrates.

Figure 2.   DRAM density evolution

In the last 10 years, DRAM density has increased in a factor of 4x. In the same time frame, NAND-based memory density has scaled 50x, as the following figure highlights:

Figure 3.   NAND density evolution

Note: This figure source is 3D NAND Technology – Implications to Enterprise Storage Applications, where more information can be found.

PMem falls in between DRAM and NAND both in terms of costs and performance, introducing a new tier of memory that is slower but with larger capacity than DRAM. It is also less expensive.

The following figure offers a roughly comparison of latency and cost for DRAM, PMem, and NAND memories.

Figure 4.   Latency and relative cost comparison for DRAM, PMem, and NAND devices

PMem can be enabled in two modes inside an ESXi host, as shown in the following figure:

• App Direct: PMem acts like a persistent memory or storage. In this mode application, the VMs can access and directly address the PMem.
• Memory Mode: PMem acts like a traditional volatile memory. In memory mode, both DRAM and PMem appear as unique tiered memory space where DRAM is used as the cache for the hottest data, with PMem providing the memory capacity. This capacity is transparent to the end user.

Figure 5.   vSphere App Direct and Memory modes for Intel PMem

Dell EMC has supported persistent memory technology from their 14th Generation of PowerEdge server release onward, while VMware announced support for PMem from vSphere 6.7 onward.

Dell PowerEdge servers based on second-generation Intel Xeon Scalable processors (Platinum and Gold grades) support a combination of DRAM and Intel Optane PMem modules. PMem modules are offered in three capacities: 128 GB, 256 GB, and 512 GB.

VxRail and Dell EMC vSAN Ready Nodes support Intel Optane Persistent Memory. Combining DRAM and PMem with different setups helps obtain comparable performance at lower costs.

There are several memory configurations that are based in Intel Optane PMem 100 and 200 series, including configurations ranging 1 TB to 12 TB of available memory as shown in the following figure:

Figure 6.   Intel Optane PMem memory configurations

Note: This figure source is vSphere Support for Intel's Optane Persistent Memory (PMEM) (67645), where more information is available.