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Western Digital Unveils 20TB HDD with OptiNAND Technology

Western Digital
(Image credit: Western Digital)

Western Digital has introduced the industry's first 20TB hard drives that integrates an iNAND UFS embedded flash drive (EFD) to improve performance, reliability, and capacity. The company's OptiNAND architecture does not use 3D NAND memory for caching, but to store various metadata to enhance key characteristics of hard drives.

Western Digital's 20TB HDDs with OptiNAND technology are based on nine 2.2TB ePMR (energy-assisted perpendicular magnetic recording technology) platters, triple-stage actuator technology for more precise positioning of read/write heads, an iNAND UFS drive of unknown capacity that uses 3D TLC NAND memory, and the company's custom system-on-chip (SoC) that controls the drive as well as communication between the HDD and the EFD. 

Modern hard drives store gigabytes of metadata on spinning media since it cannot be cost-effectively stored in local DRAM and serial NAND. HDDs store repeatable runout (RRO) metadata (the share of the position error signal that is repeatable for every spindle revolution) as well as write operations metadata at the track level to account for increased adjacent track interference (ATI). With OptiNAND, RRO and write operations are stored on the iNAND drive, which frees up space on the rotating media, faster metadata availability, and reduces the number of read/write metadata-related operations, which further improve performance (e.g., random read/write performance). Additionally, the EFD stores write operations at the sector level, which optimizes storage requirements and reduce the number of ATI refreshes to increase performance. 

As areal density of modern HDDs increases, so does the amount of metadata that needs to be stored on the drive. Also, things like ATI are affecting performance of ePMR-based HDDs stronger than before (something that can be solved with HAMR or MAMR magnetic recording technologies that are designed to greatly improve signal quality or TDMR read heads that can read data more reliably). Therefore, moving metadata from rotating media and placing it on a flash-based drive makes a lot of sense. 

In addition, the iNAND EFD can be used to store over 100MB of write cache data in case of emergency power off (EPO) event, which improves reliability of an OptiNAND-enhanced HDD. Normally, drives from Western Digital only store about 2MB of write cache data to serial flash. Furthermore, with an iNAND EFD onboard and appropriate firmware optimizations, HDDs with OptiNAND can reduce their latency.  

From a host perspective, Western Digital's OptiNAND architecture-based HDDs should work just like other drives without NAND flash. To that end, at least some customers of the company will be able to install the new drives into existing machines assuming that their 3.5-inch bays can handle slightly higher power consumption of iNAND-enhanced HDDs. Keeping in mind that Western Digital's exascale customers tend to qualify their drives before deploying, expect the drives to start shipping in high volume only several months (or even quarters) down the road.

Western Digital says that its OptiNAND technology will be used across multiple generations of its upcoming HDDs, including those based on ePMR and its successors. 

"With our IP and world-class development teams in HDD and flash, we are able to continuously push the boundaries of innovation to improve our customers’ storage infrastructure," said Siva Sivaram, president of Global Technology and Strategy, Western Digital. "We have had an extraordinary journey of HDD innovation. We changed everything with HelioSeal in 2013; were first to ship energy-assisted HDDs in volume in 2019; and now we’re going to lead again with OptiNAND technology. This architecture will underpin our HDD technology roadmap for multiple generations as we expect that an ePMR HDD with OptiNAND will reach 50TB in the second half of the decade."

The manufacturer does not say how significantly the addition of an iNAND EFD affects costs of its HDDs, but it is obvious that their bill-of-materials increases with an additional component and a high-performance SoC controller. Keeping in mind that Western Digital's OptiNAND architecture has a number of advantages over traditional HDD architectures, it is likely that the producer will charge a premium for these drives. 

  • enewmen
    I like the use of OptiNAND and ePMR , but when will 2.5" drives get updates? I can use large amounts of storage for professional work in a notebook for example. I haven't heard anything yet, not even rumors.
    Reply
  • Eximo
    enewmen said:
    I like the use of OptiNAND and ePMR , but when will 2.5" drives get updates? I can use large amounts of storage for professional work in a notebook for example. I haven't heard anything yet, not even rumors.

    8TB SSD too small or too expensive? Samsung QVO is only $700, 4TB drives under $400. Are a few 4TB 2.5" hard drives for under $200, but I'm sure they are thicker than average.

    I think the market is covered really, those that want that compact of a storage are willing to pay more.

    Mobile storage you also have large flash drives and external drive solutions to compete with.
    Reply
  • sepuko
    For people that wonder:
    "In 2008, the SDA specified Embedded SD, "leveraging well-known SD standards" to enable non-removable SD-style devices on printed circuit boards. However this standard was not adopted by the market while the MMC standard became the de facto standard for embedded systems. SanDisk provides such embedded memory components under the iNAND brand." Cred wiki
    Reply
  • waltc3
    Nice write up! See if you guys can get one of these for testing...be interesting to see! HDDs are still the only way to fly in terms of storage capacities, imo.
    Reply
  • Kamen Rider Blade
    Eximo said:
    8TB SSD too small or too expensive? Samsung QVO is only $700, 4TB drives under $400. Are a few 4TB 2.5" hard drives for under $200, but I'm sure they are thicker than average.

    I think the market is covered really, those that want that compact of a storage are willing to pay more.

    Mobile storage you also have large flash drives and external drive solutions to compete with.
    Not everbody wants to pay that much $$$ for compact bulk storage.

    There should be options for those who want 4 TB or more 2.5" HDD while being relatively small and compact.

    And QLC's durability ain't that great compared to a HDD if you're not going to use it in a "Rough & Tumble" environment.

    There's a time and place for everything, but there should be a option for us who want small 2.5" HDD's.

    And SSD's really need to shrink down to 1.8" Drive Format, 2.5" is too bulky for a modern day SSD.
    Reply
  • Eximo
    They have, called M.2. Just need to have a system with the appropriate slot.

    There are a few 4TB 2.5" drives. But that is pushing limits of density and they clearly don't sell well enough to justify many models. Decent bargain, but I would rather have the performance of 3.5" drive.

    You are basically saying you want the best hard drive technology cheap. That isn't how 'the best' usually works. You pay a premium for density. That isn't going to change. Most people can get away with 1-2TB, and that has been standard for a long while now. 500GB SSD is pretty standard on systems that don't have 2.5" bays, 1TB will probably take over in the next year or so.

    I would trust an SSD over a mechanical drive any day in a mobile device. If you are using a drive for bulk storage, write endurance shouldn't be too huge a concern. If you are continuously using a drive, there are better external options.
    Reply