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Hyperscale shift to 18 TB, SMR HDDs top '21 hard disk trends

New 20 TB energy-assisted and SMR hard disk options are starting to ship, but experts predict the top 2021 trend in data center hard drives will be the transition to 18 TB HDDs.

The hottest trends and innovations in hard disks in 2021 will center on the nearline drives that hyperscalers and cloud service providers use to beef up capacity.

Nearline 3.5-inch hard disk drives (HDDs) that spin at 7,200 RPM continue to account for the bulk of enterprise and data center shipments from Seagate, Toshiba and Western Digital, since 10,000 RPM and 15,000 RPM HDDs gave way to faster flash drives.

The highest capacity available is currently 20 TB, but industry analysts predict the transition from 16 TB to 18 TB HDDs will be the dominant trend in 2021. They do not expect to see 20 TB HDDs shipping in volume until 2022 or 2023, and price-per-TB cost declines could slow with shifts to higher capacities.

In the meantime, customers with a pressing need for the highest capacity 20 TB HDDs have options that use shingled magnetic recording (SMR) technology, for systems that write data sequentially, and energy-assisted conventional magnetic recording (CMR) technology, for random and sequential workloads. 

New long-term HDD prospects that could generate considerable debate include NVMe drives and the use of nontraditional form factors -- but products supporting those technologies will not emerge in 2021, if at all.

Below are more detailed HDD predictions for 2021 and beyond.

Recovering demand for nearline HDDs

John Chen, vice president, Trendfocus: The deployment of COVID-19 vaccines through the first half of 2021 should fuel a return to more normal economic activity. We expect corporate spending to recover and improve demand for commercial PCs/client storage as well as traditional enterprise servers and storage. This will result in the recovery of the mid-capacity 7,200 RPM nearline HDD market that services much of the enterprise OEM equipment space. Performance enterprise HDDs -- the 10K/15K RPM drives -- are on a long-term decline due to increased SSD usage, so we don't expect to see that HDD segment bounce back to pre-pandemic levels.

John ChenJohn Chen

Hyperscale expansion remains largely insulated from the negative economic impacts of COVID-19 and will accelerate in the second quarter to drive both HDD and SSD demand increases. The predominant HDD capacity shipping to tier-1 hyperscale customers through much of the first half of 2021 will center on 16 TB and transition sharply in the second half to 18 TB, which will become a relatively long-lived capacity.

The 16 TB models are all now based on 9-platter HDD platforms, and that will carry over to 18 TB. There is keen interest on the part of many hyperscale customers to either transition to a mix of 16 TB and 18 TB or move toward 18 TB HDDs, given that the additional capacity will come without the added cost of an additional disk and two heads. With the elongated 18 TB lifecycle, 20 TB CMR capacities will emerge late this year -- but 20 TB CMR drives will have little volume impact until next year.

Increasing costs for new nearline HDD models will slow the price-per-TB takedowns with each new capacity transition. Over the next couple of nearline generations, we expect designs from all vendors to eventually utilize 10 disks and 20 heads. Other components to support higher areal densities will also add cost, and this doesn't even include the additional cost to move to full energy-assisted technologies -- which promise to re-accelerate areal density increases but will likely not scale at high volumes for another couple of years.

Cloud service providers fuel growth

Edward Burns, research director, IDC: Petabyte demand for capacity-optimized HDDs will climb as companies continue to shift to the cloud. Digital transformation has become a matter of survival for nearly all companies in the face of the COVID-19 pandemic, and as a result, they were forced to make it a strategic priority. The adoption of cloud computing offers flexibility, scalability, cost efficiency and access to emerging technology, all while minimizing the risk of technology obsolescence. Companies are also concerned about business continuity planning and managing risk. They see cloud as a solution. We expect annual HDD petabyte growth for cloud service providers in 2021 to be in the mid 30% range. 

Edward BurnsEdward Burns

We also expect to see more adoption of SMR HDDs in the enterprise market in 2021, as cloud service providers (CSPs) increase their adoption of the technology due to the lower price per GB. CSPs will need to determine how to segment workloads to SMR, versus CMR, in order to store data most cost-effectively while meeting customer service level agreements in terms of latency. We should see 20 TB SMR HDDs initially shipping in 2021. SMR capacities will increase in future years as HDD suppliers find more ways to increase the capacity per disk. 

Video surveillance HDDs designed for 24-by-7 digital recording should see strong growth after a slow first half in 2020. COVID-19-related restrictions for employees at on-premises corporate locations, as well as a general lack of employees on site during the early part of the pandemic, resulted in fewer video surveillance system implementations and less interest last year.

Scott SinclairScott Sinclair

Scott Sinclair, senior analyst, Enterprise Strategy Group (a division of TechTarget): We're going to see a massive shift this year toward people buying infrastructure as a service on premises, and because of that, vendors will start to integrate more cost-effective retro media types to meet the [service level agreement] SLA. In the past, we saw this massive trend to flash for performance and simplification. Organizations wouldn't have used hard drives because they would have said, 'I don't know what my needs are. Let's just buy all flash and that way I'm covered.' But if you're buying a service, and your needs are lower, what's to stop a Dell or an HPE from saying, 'We're going to put hard drives, or tape, in the box, because it meets the SLA and it's cheaper?' You don't care. You're just paying for this SLA. You don't have to manage it. They're managing it for you.

NVMe HDDs on the way?

Raghu Gururangan, vice president of engineering, quality and strategic planning, Toshiba America Electronic Components: HDD has been the SATA and SAS interface for a very long time, but there's a lot of discussion about NVMe. There's a notion that it would simplify the storage stack, so it would benefit the industry. If you are a cloud service provider, or you have large storage subsystems, the storage software stack would be greatly simplified because SSDs are largely NVMe. There is also some advantage to getting rid of redundant layers in the hardware stack. You can attach directly to a PCIe interface. There could be hybrid arrays, where you can have SSDs and HDDs coexist in a box. How much of that is practical, and will these things come to light? Not clear. There's a healthy debate about the pros and cons from an HDD perspective. It would be a big lift to have one more interface coexist with SATA and SAS. Timeframe wise, it's hard to tell. Three to five years from now, maybe there is some traction. Not only the storage stack but also all the components in between, the boxes, have to be designed and proven and debugged. So, there's a lot of work in front of us to get to NVMe.

Raghu GururanganRaghu Gururangan

Also, cloud service providers are trying to search for a better form factor to meet their TCO metrics. The two vectors for increasing capacity are areal density and platter count. At some point, you cannot pack any more on a one-inch drive. That leads to the questions: Can I open up the form factor? What is the best way to increase the 4U box capacity that is very popular for storage? Nobody is ruling out a change to the whole form factor. In the discussions that are taking place now, it seems to be a height-oriented discussion. Height is hard enough, and if you change any other dimension, it gets even more difficult, because changing the media platter size is a non-trivial exercise. Power, performance, many things are impacted.

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