Without much fanfare, Western Digital this week introduced its first dual actuator hard drive, a 20TB drive that is designed to offer SATA SSD-like sequential read/write performance. The Ultrastar DC HS760 drive is meant to increase IOPS-per-terabyte performance for hyperscale cloud datacenters and will compete against Seagate's dual actuator Exos 2X family of HDDs. Meanwhile, Western Digital's offering will also mark the latest deployment of the company's OptiNAND technology.

The dual actuator Ultrastar DC HS760 HDD builds upon the company's single actuator Ultrastar DC HC560 drive which uses nine 2.2TB ePMR (energy-assisted perpendicular magnetic recording) platters. But in the case of the HS760, WD adds a second actuator to the drive, essentially splitting it up into two quasi-independent drives with each half having domain over 4.5 platters (9 surfaces). By doubling the number of indepent actuators, Western Digital claims that the HS760 is able to double sequential read/write speeds and increase random read/write performance by 1.7 times versus single actuator drives.

While the company yet has to upload a datasheet for its dual actuator HDD, we are looking at sequential throughput rates of around 582 MB/s, which interestingly enough is a tad faster than SATA SSDs, which max out the SATA-III at around 550 MB/s. Though it's worth noting that, as is typical for enterprise-focused hard drives, Western Digital is using Serial Attached SCSI (SAS) here, so it won't be possible to hook the drive up to a SATA host.

Since the two actuators inside Western Digital's Ultrastar DC HS760 HDD work independently, the unit presents itself as two independent logical unit number (LUN) devices, and both logical hard drives are independently addressable. This means that datacenters will have to introduce certain software tweaks (i.e., these are not drop-in compatible with infrastructure designed for single actuator HDDs). But for the added complexity on the software/configuration side of matters, data center operators are being promised not only the aforementioned higher performance levels, but also a setup that is 37% more energy efficient in terms of IOPS-per-Watt than two 10TB devices.  In essence, hyperscalers are getting many of the benefits of having two current-generation 10TB HDDs, but in a product that takes up the space of just a single drive.

The key advantage of Western Digital's Ultrastar DC HS760 20TB over hard drives with one actuator of the same capacity is significantly increased performance on an IOPS-per-TB basis. Typical enterprise-grade 3.5-inch HDDs with capacities between 8TB and 16TB offer random performance of 6 – 10 IOPS per terabyte, which is enough to ensure quality-of-service of datacenters. But at 20TB, random performance drops to less than 5 IOPS per terabyte, which requires hyperscalers to introduce various mitigations to ensure that these drives meet their QoS requirements.

Such mitigations either include implementing command queuing and latency-bounded I/O (LBIO) in firmware, usage of drives of lower capacity, reducing usable capacity per drive, or even adding sophisticated caching methods. All of these methods either increase upfront costs and/or total-costs-of-ownership. Therefore, hyperscalers need drives that can physically increase their IOPS-per-terabyte performance and dual actuator HDDs are a natural answer. As an added bonus, these hard drives also offer two times higher sequential read/write speeds than single-actuator HDDs.

As noted above, Western Digital is not the only company to offer dual actuator HDDs as Seagate has been doing this for years now. But Western Digital's Ultrastar DC HS760 has an advantage over rivals that comes in the form of its OptiNAND technology, which is an integrated iNAND UFS embedded flash drive (EFD) coupled with firmware tweaks. OptiNAND is meant to increase capacity, reliability, and performance of HDDs and while Western Digital yet has to disclose performance numbers of its Ultrastar DC HS760 drives, it is at least evident that its 20TB drive will offer more capacity than Seagate's competing Exos 2X18 18TB drive.

Otherwise, given that the HS760 is aimed primarily at hyperscalers, Western Digital is treating the drive as a product for a limited audience. Although the drive is listed on the company's website, for example, there is no public pricing listed, and buyers will have to make a sales inquiry. So the actual unit pricing on the new drive is going to vary some, depending on things like order volumes and agreements between Western Digital and its clients.

Western Digital's Ultrastar DC HS760 HDD will be covered with a five-year warranty with each LUN rated for a 500 TB annual workload.

Source: Western Digital

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  • Foeketijn - Wednesday, February 1, 2023 - link

    How long did we have to wait for this? 20 years of vaporware. And now it comes when it is only half a match against the cheapest SSD's. At least 10 years to late.
  • meacupla - Wednesday, February 1, 2023 - link

    In 2013, HDDs just started SMR and helium
    2003 was when IBM was still making HDDs
  • schujj07 - Wednesday, February 1, 2023 - link

    This is going to be used primarily in backup devices on corporate scale. The added write speed is to keep up with the all flash SANs and cut down on time to write or restore. These will cost 1/10 that if the NVMe of the same capacity so it makes sense.
  • nandnandnand - Wednesday, February 1, 2023 - link

    Datacenters were going to buy >=20 TB HDDs regardless. This just makes them slightly more tolerable if used right.
  • Samus - Thursday, February 2, 2023 - link

    20 years lol
  • Dante Verizon - Thursday, February 2, 2023 - link

    Oh unless some magical nand technology improves the cost and durability of SSDs drastically, NEVER.
  • name99 - Friday, February 3, 2023 - link

    Oh yes, the lack of durability of SSDs. The myth that will never die...

    What is going on in the minds of these people?
    - Some sort of primitivist "if it's magic I don't understand it can't possibly work reliably?"
    - Some weird belief that being "contrarian" (just like every other idiot on the internet) makes them appear wise?
    - Some desperate attempt to manipulate stocks (like Samsung or Micron are going to fall because some brave internet soul finally called their bluff on SSDs)?

    It's all very weird, the perpetual imperviousness to actual data, year after year after year.
  • Dante Verizon - Friday, February 3, 2023 - link

    MLC and SLC SSDs had decent lifespan. But from then on, life expectancy dropped in exchange for trying to lower the cost/GB and trying to keep up with HDDs, the only way so far is to increasingly reduce the life span by increasing the number of Bits/cell, another point is that in modern SSDs the complexity has also increased with more components and chips, bringing more items that can fail prematurely into the equation.

    If an SSD dies you simply lose your data. If a HDD fails you still have chances of recovery. You have no point. :P
  • schujj07 - Saturday, February 4, 2023 - link

    A data center level HDD like the WD Gold has a 550TB/year endurance rating. These are at 500TB/year. That gives us a 5 year total writes between 2500 & 2750TB. Even a lowly 1.92TB "read intensive" or 1DWPD enterprise SSD has a TBW of 3500TB.

    Sure when an SSD fails you lose your data. If you are stupid enough to not have your data backed up that is your fault. However, SSDs fail at a much lower rate the HDD.
  • eriri-el - Sunday, February 5, 2023 - link

    If you didn't go to school, you wouldn't have learned English properly and therefore understand that reliability has nothing to do with recoverability.
    Imagine having a HDD (note that I am NOT comparing to an SSD) that always fails in 3 months and you always have to replace them every 3 months, but the data is recoverable so its fine? I call that a pain in the butt.
    Go back to school and relearn your English language please.

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