For enterprise storage, persistent memory is here to stay

Persistent memory – also known as storage class memory – has tantalized data center operators for many years. A new technology promises the key to success.

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It's hard to remember a time when semiconductor vendors haven't promised a fast, cost-effective and reliable persistent memory technology to anxious data center operators. Now, after many years of waiting and disappointment, technology may have finally caught up with the hype to make persistent memory a practical proposition.

High-capacity persistent memory, also known as storage class memory (SCM), is fast and directly addressable like dynamic random-access memory (DRAM), yet is able to retain stored data even after its power has been switched off—intentionally or unintentionally. The technology can be used in data centers to replace cheaper, yet far slower traditional persistent storage components, such as hard disk drives (HDD) and solid-state drives (SSD).

Persistent memory can also be used to replace DRAM itself in some situations without imposing a significant speed penalty. In this role, persistent memory can deliver crucial operational benefits, such as lightning-fast database-server restarts during maintenance, power emergencies and other expected and unanticipated reboot situations.

Many different types of strategic operational applications and databases, particularly those that require low-latency, high durability and strong data consistency, can benefit from persistent memory. The technology also has the potential to accelerate virtual machine (VM) storage and deliver higher performance to multi-node, distributed-cloud applications.

In a sense, persistent memory marks a rebirth of core memory. "Computers in the ‘50s to ‘70s used magnetic core memory, which was direct access, non-volatile memory," says Doug Wong, a senior member of Toshiba Memory America's technical staff. "Magnetic core memory was displaced by SRAM and DRAM, which are both volatile semiconductor memories."

One of the first persistent memory devices to come to market is Intel’s Optane DC. Other vendors that have released persistent memory products or are planning to do so include Samsung, Toshiba America Memory and SK Hynix.

Persistent memory: performance + reliability

With persistent memory, data centers have a unique opportunity to gain faster performance and lower latency without enduring massive technology disruption. "It's faster than regular solid-state NAND flash-type storage, but you're also getting the benefit that it’s persistent," says Greg Schulz, a senior advisory analyst at vendor-independent storage advisory firm StorageIO. "It's the best of both worlds."

Yet persistent memory offers adopters much more than speedy, reliable storage. In an ideal IT world, all of the data associated with an application would reside within DRAM to achieve maximum performance. "This is currently not practical due to limited DRAM and the fact that DRAM is volatile—data is lost when power fails," observes Scott Nelson, senior vice president and general manager of Toshiba Memory America's memory business unit.

Persistent memory transports compatible applications to an "always on" status, providing continuous access to large datasets through increased system memory capacity, says Kristie Mann, Intel's director of marketing for data center memory and storage. She notes that Optane DC can supply data centers with up to three-times more system memory capacity (as much as 36TBs), system restarts in seconds versus minutes, 36% more virtual machines per node, and up to 8-times better performance on Apache Spark, a widely used open-source distributed general-purpose cluster-computing framework.

System memory currently represents 60% of total platform costs, Mann says. She observes that Optane DC persistent memory provides significant customer value by delivering 1.2x performance/dollar on key customer workloads. "This value will dramatically change memory/storage economics and accelerate the data-centric era," she predicts.

Where will persistent memory infiltrate enterprise storage?

Persistent memory is likely to first enter the IT mainstream with minimal fanfare, serving as a high-performance caching layer for high performance SSDs. "This could be adopted relatively-quickly," Nelson observes. Yet this intermediary role promises to be merely a stepping-stone to increasingly crucial applications.

Over the next few years, persistent technology will impact data centers serving enterprises across an array of sectors. "Anywhere time is money," Schulz says. "It could be financial services, but it could also be consumer-facing or sales-facing operations."

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