Intel recently teased a bit of new information on its 3D XPoint DIMMs and launched its first public demonstration of the technology at the SAP Sapphire conference where SAP’s HANA in-memory data analytics software was shown working with the new “Intel persistent memory.” Slated to arrive in 2018, the new Intel DIMMs based on the 3D XPoint technology developed by Intel and Micron will work in systems alongside traditional DRAM to provide a pool of fast, low latency, and high density nonvolatile storage that is a middle ground between expensive DDR4 and cheaper NVMe SSDs and hard drives. When looking at the storage stack, the storage density increases along with latency as it gets further away from the CPU. The opposite is also true, as storage and memory gets closer to the processor, bandwidth increases, latency decreases, and costs increase per unit of storage. Intel is hoping to bridge the gap between system DRAM and PCI-E and SATA storage.
According to Intel, system RAM offers up 10 GB/s per channel and approximately 100 nanoseconds of latency. 3D XPoint DIMMs will offer 6 GB/s per channel and about 250 nanoseconds of latency. Below that is the 3D XPoint-based NVMe SSDs (e.g. Optane) on a PCI-E x4 bus where they max out the bandwidth of the bus at ~3.2 GB/s and 10 microseconds of latency. Intel claims that non XPoint NVMe NAND solid state drives have around 100 microsecomds of latency, and of course, it gets worse from there when you go to NAND-based SSDs or even hard drives hanging of the SATA bus.
Intel’s new XPoint DIMMs have persistent storage and will offer more capacity that will be possible and/or cost effective with DDR4 DRAM. In giving up some bandwidth and latency, enterprise users will be able to have a large pool of very fast storage for storing their databases and other latency and bandwidth sensitive workloads. Intel does note that there are security concerns with the XPoint DIMMs being nonvolatile in that an attacker with physical access could easily pull the DIMM and walk away with the data (it is at least theoretically possible to grab some data from RAM as well, but it will be much easier to grab the data from the XPoint sticks. Encryption and other security measures will need to be implemented to secure the data, both in use and at rest.
Interestingly, Intel is not positioning the XPoint DIMMs as a replacement for RAM, but instead as a supplement. RAM and XPoint DIMMs will be installed in different slots of the same system and the DDR4 RAM will be used for the OS and system critical applications while the XPoint pool of storage will be used for storing data that applications will work on much like a traditional RAM disk but without needing to load and save the data to a different medium for persistent storage and offering a lot more GBs for the money.
While XPoint is set to arrive next year along with Cascade Lake Xeons, it will likely be a couple of years before the technology takes off. Supporting it is going to require hardware and software support for the workstations and servers as well as developers willing to take advantage of it when writing their specialized applications. Fortunately, Intel started shipping the memory modules to its partners for testing earlier this year. It is an interesting technology and the DIMM solution and direct CPU interface will really let the 3D XPoint memory shine and reach its full potential. It will primarily be useful for the enterprise, scientific, and financial industries where there is a huge need for faster and lower latency storage that can accommodate massive (multiple terabyte+) data sets that continue to get larger and more complex. It is a technology that likely will not trickle down to consumers for a long time, but I will be ready when it does. In the meantime, I am eager to see what kinds of things it will enable the big data companies and researchers to do! Intel claims it will not only be useful at supporting massive in-memory databases and accelerating HPC workloads but for things like virtualization, private clouds, and software defined storage.
What are your thoughts on this new memory tier and the future of XPoint?