WD mingles flash memory and hard drive in a single storage device

Western Digital (WD) has announced a new architecture that will combine the speed of flash memory chips and the density of hard disk drives into a single product for enterprises and consumers.

The OptiNAND technology integrates hard disk drives (HDD) with iNAND flash memory chips. WD said this will give customers on both the enterprise side and the consumer side the ability to store vast amounts more data in a bid to keep up with the exponential growth of data in the coming years. WD announced the innovations that it said break the barriers of traditional storage at its online event today.

Ravi Pendekanti, senior vice president of HDD product management and marketing at WD, said in an interview with VentureBeat that customers in areas such as hyperscale cloud, communications firms, enterprises, smart video surveillance partners, network-attached storage (NAS) suppliers, and more need a lot more capacity, performance, and reliability. And WD’s plan is to leverage the benefits of both hard drives, which can store a lot of data, and flash, which can access data quickly.

“We are confident at this time that we will reach 50 terabytes by the second half of this decade compared to 20 terabytes today,” Pendekanti said.

The brewing problem with data storage has become acute as HDD architectures now contain as much memory and processing power as PCs from the early 2000s.

In the next five years, WD expects to see more data created than twice the amount of data that has been created throughout computing history, Pendekanti said.

“To address this, we went back in and started looking at what it is that we can do next. It was about integrating NAND into our hard drives,” Pendekanti said. “What it really does is help us improve the capacity of our drives. It helps us improve the performance. And it also improves the reliability.”

Hot and warm

Above: OptiNand technology vertically integrates flash and HDD tech.

Image Credit: WD

Before OptiNAND, flash (non-volatile) memory in an HDD was used primarily for booting and storing tiny amounts of metadata. As HDD storage architecture has become more sophisticated, the addition of a flash layer is a logical step in the system’s memory hierarchy.

The teams worked on the tech for a couple of years following WD’s acquisition of flash maker Sandisk.

“We learned from some of the earlier pitfalls we mentioned,” Pendekanti said.

In the past, the hybrid solution was to write “hot” data to the limited memory of the flash chips. If it was “warm” data, it could go onto the disk itself. But it wasn’t always easy to distinguish hot from warm in terms of data that had to be accessed quickly.

“In the past, with the hybrid drives, the two technologies were brought in, but they were not fully vertically integrated,” said Carl Che, chief technology officer at the HDD business unit at WD, in an interview. “The keyword is vertical integration. And that’s where I think the biggest pitfall was. And somebody also had to understand what kind of data it was (hot or warm).”

He added, “Today, we are vertically integrating both the flash and the disk side. We are not having anyone do guesswork. And that is a big shift.”

Flash is more cost-effective than DRAM (dynamic random access memory, or main memory), with data persistence across power cycles. Flash also provides faster access than disks, enabling time-sensitive calculations to be performed while keeping the disk free to perform host operations.

The new OptiNAND-enabled memory hierarchy uses the drive system-on-chip (SoC) to control communication with the iNAND EFD. With OptiNAND, key drive housekeeping functions can take advantage of an increase in metadata capability. This can reduce future DRAM needs, as well as enabling more sophisticated mechanisms to achieve greater capacities, increased performance, and enhanced reliability.

Triple-stage actuator

Above: WD’s 20TB drive

Image Credit: WD

WD improved the precision of HDD heads with a triple-stage actuator (TSA) technology that enables better precision for a recording head on an HDD. That enables higher areal density through increased tracks per inch (TPI) to provide the highest capacities. HDDs generate gigabytes of metadata that can be utilized to increase areal density.

This data is too large to be cost-effectively maintained in DRAM, while retrieving this data on-demand from disks interferes with host operations and performance. OptiNAND enables cost-efficient storage and fast access to this massive quantity of metadata that can be stored and accessed in real time, freeing up valuable space on the rotating media for user data.

In the event of an EPO, OptiNAND can securely flush and retain nearly 50 times more customer data than prior-generation HDDs that flush data to DRAM. Meanwhile, OptiNAND technology will extend the capability of energy-assisted PMR (ePMR) for multiple generations, allowing customers to continue benefiting from a proven recording technology.

With the combined technologies, WD will be able to store 2.2 terabytes (TB) per hard disk platter, extending capacity gains on proven ePMR technology.

“We see a path to the first 3-terabyte drives using this technology,” Pendekanti said. “We are feeling confident about it.”

Setting a new industry milestone, WD has shipped samples of new nine-disk, 20TB ePMR flash-enhanced drives with OptiNAND technology to select customers. (A terabyte is 1 trillion bytes).

“All the data on the hard drive really is about maximizing the whole capacity. So this is a structure designed for future uses,” he said.

Availability

The new flash-enhanced drive architecture with OptiNAND technology will be available across the company’s portfolio of drives and storage platforms. It will also serve as the foundation for future designs and innovations, with further advances to come in intelligence, reliability, capacity, and time-to-market value. The company will begin announcing market-specific, purpose-built products across its portfolio later this year.

“We are introducing new technologies that will actually persist for multiple generations of products,” Pendekanti said. “We will focus on the technology today. And then in the months ahead, will come out and talk to us about specific products that use this technology.”