XC Core Servers and Intel Optane Persistent Memory – Memory Tiering is here !


Support for Intel Optane Persistent Memory 200 series on XC Core servers was recently announced and is now generally available on the XC650 and XC750 server models. The key advantage of Intel Optane Persistent Memory is a lower cost platform with the same memory footprint and with similar performance to a platform configured with DRAM only. This can also improve total cost of ownership by enabling higher workload consolidation rates.


To support this announcement, I thought I would cover the basics of Intel Optane Memory technology, what exactly is Intel Optane persistent memory and, more to the point, and why should you care!


Firstly, Intel Optane Technology is offered in two forms and the below diagram from Intel does a great job of illustrating where both Optane technology offerings sit in the overall performance hierarchy for storage mediums.


At the top we have DRAM technology offering the fastest access speeds at the highest cost per Gigabyte (GB). Next, Intel Optane Persistent Memory sits just below DRAM in terms of performance bridging the gap between traditional memory and SSD storage tiers. In essence Intel Optane Persistent Memory adds an additional memory tier between DRAM and SSD. The benefit of this tier is twofold, firstly (and the hint is in the name !) Intel Optane Persistent Memory can be configured to be non-volatile addressable storage (called app direct mode) offering a DRAM like high-speed persistent storage tier at a lower cost, or secondly as tiered cost-effective volatile memory (called memory mode) where the DRAM acts as a cache and the Intel Optane persistent memory provides the large memory capacity.


Next, in terms of performance we have Intel Optane SSD’s which offer faster storage access over traditional NAND SSD. I’m not going to cover Optane SSD’s or the technology in this article as this posts aim is to focus on Optane Persistent Memory, suffice to say, Intel Optane SSD’s are ideal for fast caching or tiering of hot data should you applications / workloads require the performance Optane SSD’s can provide.


Let’s get back to the star of the show.


Intel Optane Persistent Memory enables a tiered memory architecture.


Ok, why should you care ! To me this is the exciting piece. Data tiering is the process whereby data is shifted from one storage tier to another as its state changes dynamically from hot to cold and vice versa with the aim of reducing expensive storage costs via caching, thus increasing efficiency.


The concept of data tiering is not new. Hot and cold data is tiered to great benefit, from CPU architectures right down the stack to various storage mediums, however a DRAM efficiency never formed part of that tiering architecture or pipeline. Now these same benefits can be brought over to memory, turning the traditionally DRAM only legacy architecture to a tiered memory architecture of DRAM acting as the cache tier and Intel Optane Persistent Memory as the capacity tier, again offering tremendous benefits.


The key advantage of Intel Optane Persistent Memory is a lower cost platform with the same memory footprint with similar performance to a platform configured with DRAM only. This can also improve total cost of ownership by enabling higher workload consolidation rates.


The below graphic shows how Intel Optane persistent memory can be implemented to reduce DRAM costs while not sacrificing performance for a 150 VM’s VDI workload. Again, thanks to Intel for providing me this slide.


Comparing a DRAM only config on an Intel Xeon Gold 6342 CPU with 1TB of DRAM to 1TB Optane sees similar latency with an overall lower cost per VM.


Initially on XC Core servers, only Memory Mode will be supported. App Direct Mode is not supported yet and will be coming in the near future, so, to that point I wont focus on the benefits of App Direct mode until it’s supported


Intel Optane Persistent Memory modules are installed in the memory channel in the DDR4 DRAM form factor and can be combined with conventional DDR4 DIMMs. Each socket supports one to eight modules.


The current supported configuration is 16 x16G + 8x 128GB Intel Optane Persistent Modules offering a tiered memory config of 1.25TB (only 1TB visible to Nutanix as the 256GB of DRAM is used as cache) at a recommended 4 to 1 ratio (as above). Intel 3rd Generation “Ice Lake” Gold or Platinum CPUs are required. ESXi 7.0U2 or greater is supported with support for AHV coming soon. Be sure to check here as further configurations and modes are added.


For illustration purposes I have included a memory population diagram, note: Only one CPU is shown for simplicity – the configuration of the 2nd CPU is identical.

Be sure to check back here as more configurations come on-stream and for those of you interested more information on Intel’s memory tiering architecture can be found here.



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