WD Reveal the Ultrastar DC HS760 Dual Actuator 20TB Hard Drive

The WD Dual Actuator Ultrastar HS760 20TB HDD Revealed

When it comes to storing large amounts of data in a data center or even a single large-scale server rack array, having larger capacity hard drives is essential to achieve better Total Cost of Ownership (TCO). However, with many applications requiring access to frequently used warm data, traditionally more affordable but slower mechanical HDDs have begun to present a bottleneck – with many highlighting the glass-ceiling performance of traditional single actuator (the arm that reads the platters) drives starting to become the end of the road! Although WD is not the first to discuss and research into confronting this bottleneck (more on that later), the newly revealed Ultrastar DC HS760 is Western Digital’s solution to this issue, delivering high performance and high capacity for demanding data center applications, whilst maintaining the things that have made the Ultrastar series a continued popular choice in data centers worldwide. But what exactly is a dual actuator HDD? Why does that subject sound so familiar? And is this a new kind of HDD technology (alongside EAMR and MAMR) that you need to keep an eye on? Let’s discuss.

Key Hardware Highlights

What is Dual Actuator Technology and Why is it a Big Deal?

Dual actuator hard drives are a type of hard drive that utilizes two independent actuators to read and write data. An actuator is a device that moves the read/write heads of a hard drive in order to access data stored on the disk platters. In a dual-actuator hard drive, two independent actuators are used to move the read/write heads, allowing for faster access times and improved performance. For example, technically, a 16TB Dual Actuator equipped HDD is actually two 8TB HDDs that are inside the same HDD casing space, sealed by helium to ensure that thinner platters can be used, significantly reducing friction/drag potential.

The Prototype of the dual-actuator Western Digital Disk, which was first revealed at the March 2019 Open Compute Project Summit Event.

The two actuators are connected to separate motors, which can be independently controlled by the hard drive’s controller. This allows for more precise control over the movement of the read/write heads, resulting in faster access times and improved performance. The Ultrastar DC HS760 is a 20TB dual actuator CMR HDD that leverages Western Digital’s 2.2TB/disk density platters (as seen in their recent 20TB and 22TB releases in WD Red, WD Gold and Ultrastar). The two independent actuators that can simultaneously read or write data, providing up to twice the sequential performance. With each 10TB LUN appearing as an independent storage volume, the host application can manage file placement between the two volumes, improving access density (IOPS/TB). The benefits of a dual actuator include up to 2x sequential throughput, up to 1.7x random performance, and up to 37% more power efficiency. WD Are still yet to confirm the precise performance stats (and these percentage improvements come directly from their own product pages) but given the higher-end nature of their end-user base, the SAS interface on these drives (which might open up in future generations to SATA) and implementation of other elements of the Ultrastar DC drive series technology (eg OptiNAND), then I would not really doubt their commitment to these numbers. But, haven’t we heard about dual actuators in HDDs before?

How are the WD Dual Actuator Ultrastar DC HS760 and Seagate EXOS Mach.2 Drives Different?

We somewhat need to address the dual actuator-equipped elephant in the room! Back in 2019/2020, Seagate made quite a splash when they revealed their EXOS Mach.2 series of HDDs. These eventually rolled out commercially in 2021 in 14TB and 16TB versions, the Exos 2X14 consisted of two 7TB hard drives housed in a single hermetically sealed, helium-filled 3.5-inch chassis. It had a 7200 RPM platter speed, a 256MB multisegmented cache, and a single-port SAS 12Gb/s interface. The host system viewed the Exos 2X14 and 2X16 as two separate and independently addressable drives when connected. In full utility, it boasted 524MB/s sustained transfer rate. Originally designed to challenge the difficulty of choosing between cheap-large-slow HDDs or expensive-small-fast SSDs at the data center level. Fast forward to 2023 and we now have additional 16TB and 18TB Seagate EXOS Mach2 drives, in the 2X16 and 2X18 respectively. So what sets the Western Digital DC HS760 HDDs apart from these Seagate Mach.2 Drives?

Although both drives are designed for the enterprise market (so 55TB Workloads and 2.5M hours MTBF is quite standard and comparable with their single actuator counterparts), the WD drive also includes OptiNAND (Something we discussed HERE in our WD Red Pro 22TB Review last year). OptiNAND Technology The Ultrastar DC HS760 utilizes Western Digital’s proven OptiNAND technology, which integrates an iNAND Universal Flash Storage (UFS) Embedded Flash Drive (EFD) with traditional spinning disk media. This allows the drive to have better performance and data protection compared to traditional drives. Additionally, the WD Ultrastar DC HS760 also arrives with ArmorCache, a feature enabled by OptiNAND, which offers the best of both write cache enabled (WCE) and write cache disabled (WCD) modes. In the event of an EPO, the DRAM cache will be safely written in either mode, ensuring data protection and comparable performance across both WCE and WCD modes. Until Western Digital release further information on these new drives (official data sheets and/or live demonstrations) we will have to wait a little longer for more information on the abilities of these new high-performance SAS drives.

Are Dual Actuator HDDs Better or Worse than 10K or 15K RPM HDDs in Speed or Storage?

Dual Actuator HDDs aim to solve IOPS/TB constraints in systems that are currently using high-capacity 3.5-inch nearline HDDs, whereas 10K/15K mission-critical HDDs (such as the WD Velociraptor of the past) have much smaller capacities of around 2.4TB/900GB top capacities, respectively and are intended for servers. 10K and 15K hard drives differ from dual actuator hard drives in the way they access data on the disk platters. 10K and 15K hard drives use a single actuator to access the data on the disk platters, but do so up to twice as fast as dual actuator HDDs. However, dual actuator drives can handle more input/output operations per second, making them a good choice for demanding applications. There is the negligible benefit of Improved data integrity (i.e If one actuator fails, the other can still access the data on the disk platters, reducing the risk of data loss), but the main benefit/difference is that the dual arms allow a greater frequency of access in read and write overall. The popularity of 10K and 15K HDDs has dropped noticeably in recent years, thanks in part to the improvements NAND durability in SSD technology making them significantly more acceptable in warm/hot data archives – though they cannot hit the capacity of HDDs (NAND costs and physical PCB space), so dual Actuator HDDs are WD’s response to this growing disparity!

When will the WD Ultrastar DC HS760 HDD Be Available?

Although WD Ultrastar DC HS760 Hard Drives have been revealed, it is still very early! They have been listed on the company’s official store, but no price has been provided at this time (as well as no datasheet being made available at this time). Most likely, the first wave of units being made available will be extended to existing data centers (likely already well underway) and as this is a highly data-center class HDD, it will be surprising if this HDD is widely commercially available for a while yet! Watch this space and hopefully, we will get a chance to review this remarkably exciting HDD later in 2023 here on NASCompares.

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