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The perfect union: NVM Express, Storage Class Memory and HPE Nimble Storage


HPE Nimble Storage SCM NVMe_blog.jpgWhich technologies will power the next wave in storage? And how can you prepare today for what is coming tomorrow? See what answers HPE Nimble Storage has in store.

First, SCM and NVMe explained

SCM and NVM Express (NVMe) are key technologies powering the next round of improvements in storage array performance. Of the two, the emergence of new Storage Class Memory (SCM) technology is perhaps more significant, with 3D XPoint and Z-NAND memory leading the way.

These SCM media enable faster solid-state drive (SSD) access times versus those possible with standard NAND flash memory. NVMe in turn provides a needed improvement in the protocols used to access storage devices, substantially reducing the overhead of accessing high-performance SSDs.

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The promise of NVMe

The NVMe storage protocol offers benefits over SAS and SATA. NVMe runs directly over PCIe, eliminating conversion costs and queuing points inherent in bridging to legacy storage interconnects. Direct PCIe access also avoids serialization bottlenecks that limit interconnect utilization with SAS and SATA. The NVMe host interface is designed to maximize CPU efficiency in performing I/O. Avoiding translation steps improves device latency. Increasing efficiency and concurrency enables higher IOPS.

Although NVMe SSDs have been available for a few years, they’ve not yet been deployed in the most cost-effective storage arrays. That’s because high availability RAID groups of SAS-connected SATA SSDs deliver plentiful throughput with superior economics and scalability versus high availability solutions using NVMe SSDs. As NVMe economics and scalability catch up, storage arrays will shift to take advantage of its relative strengths.

How does SCM fit in?

The term Storage Class Memory encompasses a number of solid-state storage media types researched starting more than a decade ago. These media vary widely in their fundamental physics, structure, and properties, but all seek to improve in one or more characteristics on legacy flash memory and DRAM. A few SCM types have been commercialized. Two stand out due to superior density and cost versus DRAM, combined with faster access versus legacy NAND flash: 3D XPoint memory and Z-NAND flash memory.

3D XPoint memory developed by Micron and Intel is a novel media available in NVMe SSDs today, and in the future in Persistent Memory attached to CPU memory buses. Samsung’s Z-NAND flash memory is derived from its legacy 3D NAND flash media, but delivers SCM-class performance and endurance, available in NVMe SSDs.

We at HPE believe that future storage arrays will support SCM and NVMe to make the most of storage technology evolution. Relative to a typical flash SSD, reads from an SCM SSD will complete roughly 10x faster at low to moderate utilization and tolerate 10x more write cycles before wear out, but may be 10x more expensive per gigabyte. Given the large difference in price and performance, it is more beneficial in early generations to combine flash and SCM SSDs such that flash is used for durable storage and SCM is used to cache frequently accessed data and metadata. This reduces read access times for hybrid flash and SCM systems significantly versus pure flash systems. As the cost of SCM media falls, we expect the industry will increasingly use it for durable storage as well.

SCM and NVMe: a marriage made in heaven

Our near-term goal with HPE Nimble Storage is to use the combination of NVMe and SCM to create an NVMe-connected low-latency read cache. We already have the best hybrid flash array technology in the industry, so we have an ideal foundation for “hybrid SCM” all-flash arrays. With HPE Nimble Storage hybrid flash arrays, SSD is used as a cache for HDDs with the performance efficiency to deliver flash-based performance for most IO operations. Just as SSD-based cache in our hybrid flash arrays deliver dramatically better response times than pure HDD arrays, an SCM-enhanced Nimble Storage All Flash Array based on this hybrid technology will deliver response times that are simply not attainable with today’s all-flash architectures.

Although NVMe-connected SCM SSDs could be used as the primary storage media in NVMe-based storage arrays, we expect that the cost of these “all SCM arrays” will remain prohibitive for most use cases for some time to come. In the meantime, SCM-accelerated all-flash arrays solutions will marry the performance benefits of SCM with the lower cost of flash.

HPE Nimble Storage delivers

Based on these principles, we just announced the next generation of HPE Nimble Storage all-flash and hybrid flash arrays. This platform is designed to deliver the perfect marriage of NVMe and SCM while addressing the investment protection and non-disruptive upgrade concerns of customers. All-flash arrays purchased today will support upgrades to exploit these new technologies without forklift replacement or disruptive downtime. These new product capabilities complement our strategy to support NVMe/SCM on our 3PAR platform. Rest assured that your HPE Nimble All Flash Arrays are designed to seamlessly take advantage of next-generation storage protocols and next-generation media while preserving your investment in the new HPE Nimble Storage flash platform.

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Meet Around the Storage Blog bloggerJeff Kimmel, HPE Nimble Storage CTO. Jeff focuses on applying new technology to HPE Nimble’s best-of-breed data storage solutions, along with guiding continuous product improvement and extensions to increase customer value and respond to evolving market opportunities. He has an extensive record of innovation in enterprise systems and data storage, reflected in a portfolio of 80 U.S. patents.

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Our team of Hewlett Packard Enterprise storage experts helps you to dive deep into relevant infrastructure topics.


Great overview and update Jeff!  Something I find often misunderstood about the SCM and NVMe story is the importance of having a NVMe supported infrastructure to connect to these next generation storage systems.  Fortunately, HPE's Gen6 StoreFabric switches, directors, and HBAs are ready to support NVMe over Fibre Channel.  Without the supporting infrastructure, hosts wouldn't be able to fully take advantage of these new technologies.