Persistent Memory is bringing a revolution in performance, cost and capacity that will change server, storage system, data center and software design over the next decade. This article describes some ways storage vendors are integrating persistent memory into enterprise storage systems in 2019.
Intel Optane DC Persistent Memory Modules (PMM)
As noted in the second article in the series–NVMe-oF Delivering While Persistent Memory Remains Mostly a Promise—the lack of a standard DIMM format for persistent memory is a key barrier to the development of NVDIMMs. Nevertheless, Intel recently announced general availability of pre-standard Optane DIMMs, branded Intel Optane DC Persistent Memory Modules (PMM).
Intel supports multiple modes for accessing Optane PMM. Each mode exposes different capabilities for systems to exploit. In “Memory Mode” DRAM acts as a hot-data cache in front of the Optane capacity tier. Somewhat strangely, in memory mode the Optane provides a large pool of volatile memory. A second mode for Optane PMM is called “App Direct Mode”. In App Direct Mode, Optane is persistent memory, and applications write to the Optane using load/store memory semantics.
NetApp demonstrates one way this technology can be integrated into existing enterprise storage systems. It uses Optane DIMMs in application servers as part of the NetApp Memory Accelerated (MAX) Data solution. MAX Data writes to Optane PMM in App Direct Mode as the hot storage tier. The solution tiers cold data to NetApp AFF all-flash arrays. With NetApp MAX, applications do not need to be rewritten to take advantage of Optane. Instead, the solution presents the Optane memory as POSIX-compliant storage.
Storage Vendors are Using Optane SSDs in Multiple Ways
As noted in the first article in this series, multiple storage system providers are taking advantage of Optane SSDs. Some storage vendors, such as HPE, use the Optane SSDs to provide a large ultra-low-latency read-cache. Some vendors, including E8 Storage, use Optane SSDs as primary storage. Still, others use Optane SSDs as the highest-performing tier of storage in a multi-tiered storage environment.
A startup called VAST Data recently emerged from stealth. Its solution uses Optane SSDs as a write buffer and metadata stored in front of the primary storage pool. It uses the least expensive flash memory–currently QLC SSDs–as the only capacity tier. The architecture also disaggregates storage processing from the storage pool by running the logic in containers on servers that talk to the storage nodes via NVMe-oF.
MRAM is Being Embedded Into Storage Components
At the SNIA Persistent Memory Summit, one presenter said that the largest uses of MRAM in the data center are enterprise SSDs, RAID controllers, storage accelerator add-in cards, and network adapters. For example, IBM uses MRAM in its Flashcore Modules, its most recent generation of 2.5-inch U.2 SSDs. The MRAM replaced supercapacitors plus DRAM used in the prior generation of SSDs, simplifying the design and enabling more capacity in less space without the risk of data loss.
Persistent Memory Will Impact All Aspects of Data Processing
Technology companies have invested many millions of dollars into the development of a variety of persistent memory technologies. Some of these technologies exist only in the laboratories of these companies. But today, multiple vendors are incorporating Intel’s Optane 3D XPoint and MRAM into a variety of data center products.
We are in the very early phases of a persistent-memory-enabled revolution in performance, cost, and capacity that will change server, storage system, data center and software design over the next decade. Although some aspects of this revolution are being held back by a lack of standards, multiple vendors are now shipping storage class memory as part of their enterprise storage systems. The revolution has begun.
This is the third in a series of articles about Persistent Memory and its use in enterprise storage. The second article in the series is NVMe-oF Delivering While Persistent Memory Remains Mostly a Promise.
This article was updated on 4/5/2019 to add a link to the prior article in the series.