Hard Drive Capacity And The Race Beyond 20TB
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In the race for higher hard drive capacity, reaching 20 terabytes is a big deal. Demand for data storage is growing sharply, and businesses need a place to park the bytes.

Finally, after several years of industry speculation, all three drive manufacturers are either shipping—or close to shipping—limited numbers of 20TB drives.

2020 will be remembered for many things. From an industry perspective, the arrival of the 20TB hard drive will be one of them.

Seagate And the Path To 20TB

These journeys take time. Seagate started talking seriously about the feasibility of reaching 20 terabytes as far back as 2013, according to CEO Dave Mosely.

Even that was something of a step back from previous expectations. In the 2000s, Seagate chief engineer Mark Kryder foresaw reaching 40TB by 2020 and downplayed the long-term capabilities of solid-state drives.

For HDD, the reality was a much bumpier ride.  The acceleration in areal density—the concentration of bits stored per square inch of media—slowed during the 2010s.

But progress didn’t stall. Hard drive makers turned to add platters to each device to boost storage capacity. Increment jumps of two terabytes became the norm.

The strategy paid off. Seagate launched its first 6TB drive in 2014 and its first 18TB drive just six years later.

While this may not match the rapid acceleration foreseen in Kryder’s law, a tripling in capacity across a six-year period is hardly shabby. And while 2020 may not be the year of 40TB, the prospect of mega-capacity devices remains on the cards. Only time will tell how quickly we arrive there.

Western Digital Hedges Its Bets

By contrast, Seagate rival Western Digital initially touted MAMR (microwave-assisted magnetic recording) technology as the optimal solution to the challenge of areal density. But the firm is now squarely hedging its bets.

By the end of 2019, WD had itself been investing in HAMR development (reportedly to the tune of $500 million) alongside its MAMR initiative.

Milligan’s successor David Goeckeler has continued down this path. Speaking to investors in September, he doubled down on the company’s position that it’s not MAMR vs HAMR but an “all-of-the-above” approach.  Neither is it about expanding capacity at any cost. Instead, what makes the most sense economically and commercially will guide the way forward.

Nor is it only about developments in energy-assist technologies such as HAMR and MAMR. Advances in actuator technology and firmware are among several ways of driving density, Goeckeler remarked.

Western Digital is certainly working hard to squeeze as much technology as possible into its new devices. In introducing its first 20TB drives to cloud storage providers like Dropbox, WD used a combination of energy-assist technology, helium sealing, and shingled magnetic recording.

Toshiba Plays Catch Up

Similar to Western Digital, Toshiba is using a mix of SMR, TDMR (two-dimensional magnetic recording), and MAMR technologies to support increased capacities in its hard drive road map. But unlike WD, it has yet to release a 20TB drive.

Instead, it announced in November it was sampling an 18TB MAMR HDD with select customers. A 20TB drive remained in the plan for FY2021, in line with its initial road map, Toshiba said.

One way Toshiba may transition from 18TB to 20TB is to add a tenth platter to the drive. The development of thinner glass substrates (needed for heat-assisted magnetic recording) may allow more platters to fit into the 3.5-inch form factor.  

Importantly, Toshiba is committed to increasing its market share for nearline hard drives, where it is playing catch up to its competitors Seagate and Western Digital. The firm hopes to expand its share of the nearline HDD market from 12% to 20% by the end of FY21.

Nearline is where the bulk of HDD revenue is expected to fall in the next five years. Sales of consumer hard drives will almost entirely evaporate in favor of the performance benefits of SSD.

Beyond 20TB

20 terabytes may have been a long time in the making, but the hard drive manufacturers are eager to maintain the quest for mega capacity gains.

Seagate, which of the three makers has its fortunes most directly tied to HDD, is particularly OutFront on this point? CEO Mosley says the company already can build 24TB drives in the lab. And he remains confident that HAMR technology will eventually enable much larger capacity jumps than presently the case.

“[The technology] really allows capacity jumps of 10 terabytes or even more,” said Mosley to investors in November. “So, we should get to 30 and 40 and 50 terabytes someday. This is what the world needs to run data centers more and more efficiently.”

And he insisted that HAMR, rather than MAMR, is the right technology to achieve significantly higher future capacities per device. “We know MAMR really well. It’s a viable technology, but it’s a small turn of the crank.”

Nonetheless, he acknowledged that the development costs of HAMR technology would take time to recoup. Significant shifts in TCO would not kick in until capacities hit the mid-20 terabytes.

Embracing Innovation

While HAMR may be the long-term play, it is not one single technological development that will usher in the era of massive capacities envisioned by Kryder’s law.

Instead, a range of engineering and software innovations are required to support and enhance the steep climb up Higher Capacity mountain.

Supporting technologies on the path to mass capacity include:


RefInements in recording technology:

There is a number of approaches on the table here. For example, shingled magnetic recording (SMR) utilizes the partial overlaying of tracks to increase areal density by 25%, but with performance limitations.

Two-dimensional magnetic recording (TDMR) relies on multiple read elements to generate a stronger signal-to-noise ratio. TDMR delivers a 20% boost in areal density over PMR but comes at an increased cost.


Improvements in media capabilities:

Japanese platter manufacturer Showa Denko announced back in February the development of new HD media. Designed for HAMR, these platters pave the way for HDD capacities as high as 80TB, it claims.

Meanwhile, substrate maker Hoya says that HAMR technology is essential to achieve higher drive capacities beyond 20TB.


Engineering enhancements:

Multi-actuator arms use two sets of read-write heads that logically divide a disk drive into two halves and perform read/write operations simultaneously to increase overall input/output.


Protocol and software development:

Both Western Digital and Seagate have embraced open-source RISC-V processor designs to better support the compute demands that mass capacity storage will bring.

Moreover, development work is afoot to extend the flash interconnect protocol NVMe to HDD. If successful, this promises to extend some of the massive parallelism enjoyed in flash-native environments to hard disk drives, with their traditionally slower data transfer rates.


Driving Market Tensions

Of course, the manufacturers have a vested interest in talking up the potential for massive capacity increases.

But the march toward greater capacities is not slowing up any time soon. Higher capacities are essential to preserving HDD’s cost advantage over SSD in the data center.

And it is in the fault lines between HDD and SSD that we see the industry battle play out. Seagate, heavily dependent on spinning media, believes HDD will retain its price advantage over SSD until at least the middle of the 2030s.

By contrast, Western Digital insists its growth investment in flash remains strategically correct.

Nonetheless, he recognizes that HDD remains critical to meet exploding demands for data storage. “Storage is the fundamental underpinnings of the digital economy we live in. Continuing to drive the roadmap of hard drives is extremely important. [HDD] is the storage of the public cloud and it’s going to be for a long time to come.”

Toshiba, doubling down on its nearline production, shares this view. Hard drives remain the most commercially viable way to store data at scale “based on current price points and future price projections.

For each of the manufacturers, the race for increased hard drive capacity is real. For as long as serious market demand exists, the trio will run hard and fast in pursuing additional terabytes.


Author: Horizons Technology