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Western Digital 20TB UltraStar DC HC560 Review

The explosive growth in data center storage demands is putting enormous pressure on hard disk manufacturers to deliver ever higher capacities. Western Digital (WD) has consistently shown it is up to the challenge and in this review we test its high-capacity 20TB UltraStar DC HC560 model.

Designed to satisfy a wide range of data center duties, the DC HC560 targets demanding applications such as hyperscale and cloud storage, distributed file systems, massive scale-out projects and bulk storage plus primary and secondary storage for big data analytics. WD offers models with SATA III or SAS3 interfaces plus SED (self-encrypting drive) options, and along with a range of innovative features aimed at improving reliability, performance, and power consumption, the DC HC560 introduces WD’s new OptiNAND technology.

Western Digital UltraStar DC HC560

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UltraStar DC HC560 Hard disk features

Whereas WD’s 20TB Red Pro model is restricted to use in NAS appliances with up to 24 bays, the DC HC560 is aimed at massive, rack-dense storage arrays and so has none of these restrictions. These 7,200rpm spinners are, as expected, helium-filled, and WD’s HelioSeal technology ensures they stay completely sealed and contaminant-free.

HelioSeal hermetically seals the hard disk chassis thus avoiding issues common with air-filled drives which usually require a breather hole in their casing. By using helium inside the drive, HelioSeal is able to decrease turbulence and buffeting, allowing the actuator arms to be more precisely positioned as vibration and platter movement at high revolutions are significantly reduced.

The DC HC560 employs all of the same innovative technologies that were introduced in the 18TB DC HC550. TDMR (two-dimensional magnetic recording) heads are still in evidence but the drive mechanics have seen significant improvements.

When it launched the DC HC550, WD claimed an industry first with a new triple-stage actuator (TSA). This employs three pivot points so it can position the read-write heads more accurately on tracks allowing them to be placed closer together thus resulting in more tracks per inch (TPI) and a greater areal density.

Another unique technology present in the DC HC560 is WD’s ePMR (energy-assisted perpendicular magnetic recording) which is collectively grouped under the EAMR (energy-assisted magnetic recording) heading. Essentially, ePMR sends an electrical current to the write head to produce an additional magnetic field and by producing a more consistent write signal and significantly reduced jitter, it allows BPI (bits per inch) and areal density to be increased even further.

The DC HC560 incorporates many of the well-established features you’d expect to see in a drive designed to operate continuously in large multi-drive storage arrays. Issues with excessive vibration are countered with top and bottom attached spindle motors while WD’s rotational vibration safeguard (RVS) technology uses sensors placed on the edges of the hard disk’s circuit board allowing the drive’s actuator to compensate by precisely controlling the head position.


Combining these technological attributes with WD’s OptiNAND shows clear advantages over the competition. The DC HC560 is still able to use 9 platters and 18 read/write heads – Seagate’s 20TB IronWolf Pro and Exos X20, for example, both required an increase to 10 platters and 20 read/write heads.

WD’s OptiNAND technology integrates an embedded iNAND flash drive on the hard disk’s mainboard and provides enhancements to its SoC (system on chip) and firmware algorithms. Put simply, OptiNAND is used to store operational and housekeeping metadata – previously much of this had to be stored on the platters.

WD is at pains to point out that this is not a hybrid technology as the flash memory is only used to offload large quantities of metadata and not user data. Moving metadata to flash memory means it can be accessed faster, there’s more room on the platters for user data and it provides a 100MB cache that during an emergency power-off event, can be used to flush data to – at least 50 times more than previous generations of hard drives.

Lab test setup

The UltraStar 20TB DC HC560 is designed for use in multi-drive RAID arrays so there’s little to be gained by testing a single drive in a PC. For real-world performance testing, we used Qnap’s TVS-882BR which is an 8-bay high-end desktop appliance equipped with a 3.6GHz quad-core Intel Core i7-7700 CPU and 32GB of DDR4 memory.

ATTO Celerity FC-164P HBA with quad 16Gbps FC ports + QNAP’s TVS-882BR + 4 x DC HC560 SATA Drives

The Qnap system software and apps were loaded on a dedicated mirrored array comprising two enterprise-class 1.92TB Micron 5200 Max SATA SSDs. For performance testing, we fitted four 20TB DC HC560 SATA models and created a dedicated RAID5 storage pool.

As Qnap provides fiber channel support as standard, we opted to use this for high-performance testing and installed an ATTO Celerity FC-164P HBA with quad 16Gbps FC ports in the appliance. Our test host was a Dell PowerEdge T640 tower server equipped with dual 2.1GHz 22-core Xeon Scalable Gold 6152 CPUs, 384GB of DDR4 plus an ATTO Celerity FC-164P HBA and running Windows Server 2019.

We created a dedicated 1TB FC LUN on the test drive array and mapped it to the server over a dual-port 32Gbps MPIO FC connection. Tests were conducted using Iometer configured with 256KB transfer request sizes for testing maximum sequential and random read/write rates and 4KB request sizes to measure IOPS throughput.

UltraStar DC HC560 Performance analysis

Testing the UltraStar 20TB DC HC560 drives in a RAID array and over high-performance fiber channel connections to a host system allowed us to see how they behave in a real-world business environment. Also, this is exactly the same lab environment and RAID configuration used to test the 18TB data center drives from WD, Seagate, and Toshiba so we could directly compare performance results.

The DC HC560 claims a maximum sustained single-drive transfer rate of 269MB/sec which is identical to WD’s 18TB DC HC550. These numbers are in the same ballpark as Seagate’s Exos X18 and slightly lower than Toshiba’s MG09 18TB which quote 270MB/sec and 281MB/sec respectively.

Our tests show clearly that the DC HC560 is capable of delivering an impressive performance that easily matches and in some areas, exceeds the competition. In our Iometer sequential read test, the DC HC560 delivered impressive speeds of 3,151MB/sec and moved slightly ahead for sequential write operations with 3,149MB/sec.

DC HC560 is capable of delivering impressive performance

For random read performance, the DC HC560 delivered almost identical results to all the 18TB drives. Our 100% random write test is a worst-case scenario as few businesses will have these kinds of workloads but we found the DC HC560 returned very similar results to the rest.

WD also posted excellent results in our throughput tests. Sequential read and write rates were measured at a steady 303,300 IOPS and 238,900 IOPS while random read and write tests returned 300,800 IOPS and 3,290 IOPS.


As data center demands increase exponentially, hard disk manufacturers need to be ever more creative as they search for ways to allow organizations to increase capacity within the same storage footprint. Traditional PMR (perpendicular magnetic recording) technology is reaching the upper limits of capacities but with the introduction of an impressive range of industry firsts, WD is squeezing even more capacity into standard 3.5in. format hard disks.

Along with all the new features introduced in the previous generation, the 20TB UltraStar DC HC560 is WD’s first data center drive to implement its smart OptiNAND embedded flash memory. This has clear benefits for increased capacity now and into the future, and our real-world lab tests confirm that the DC HC560 SATA model delivers excellent performance.

Reliability is assured with the same 2.5M hour MTBF plus 550TB yearly workload rating as the competition and WD also backs this up with a generous 5-year limited warranty. The 20TB UltraStar DC HC560 is a great choice for enterprises with demanding workloads plus big storage requirements and at around $420 per unit, is outstandingly good value.

9.6Expert Score
WD HC560 Delivers Good Value

The 20TB UltraStar DC HC560 is a great choice for enterprises with demanding workloads plus big storage requirements and at around $420 per unit, is outstandingly good value.

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