Rapidly growing storage demands in the data center and cloud are driving intense competition between all hard disk manufacturers as they strive to meet this ravenous appetite. Western Digital (WD) now steps up to the front of the pack by being the first manufacturer to deliver a complete family of 22TB hard disks based on the tried and tested CMR (conventional magnetic recording) technology.
They cover the entire spectrum of business usage scenarios with the Red Pro HDDs designed for NAS appliances with up to 24 bays. The Purple Pro focuses on surveillance and is designed to handle continuous sequential write operations as used by IP camera recording applications while the Gold targets enterprise data center applications requiring a low-cost SATA interface and receives a firmware tweak to increase performance.
In this review, we test WD’s flagship 22TB UltraStar DC HC570 which is geared up to handle demanding applications such as hyper-scale and cloud storage, distributed file systems, massive scale-out projects, and bulk storage plus primary and secondary storage for big data analytics. Whereas all the other ‘colors’ are only available with SATA interfaces, the DC HC570 comes in SATA or SAS3 models, offers standard and SED (self-encrypting drive) versions, and a choice of 512e (emulation) and 4Kn (native) sectors for both interface types.
DC HC570 Hard disk features
The DC HC570 doesn’t have any of the storage array population restrictions as imposed on NAS-specific models and is designed to be used in massive, rack-dense systems. Spin speeds stay at 7,200rpm and helium gas remains the filling of choice with WD’s HelioSeal technology ensuring 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. As helium is less dense, it decreases turbulence and buffeting, allowing the actuator arms to be more precisely positioned as vibration and platter movement at high revolutions are significantly reduced.
You’ll also find the same set of innovative technologies that were introduced in WD’s 18TB DC HC550. TDMR (two-dimensional magnetic recording) heads are still in evidence but the drive mechanics have been significantly improved.
WD claimed an industry first with its triple-stage actuator (TSA) when it introduced it in the DC HC550. Using three pivot points, it can accurately position the read-write heads on tracks so they can be placed closer together to deliver more tracks per inch (TPI) and a greater areal density.
WD’s ePMR (energy-assisted perpendicular magnetic recording) is another unique technology present in the DC HC570 and this is collectively grouped under the EAMR (energy-assisted magnetic recording) heading. This sends an electrical current to the write head to create 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.
Vibration in multi-drive storage arrays and appliances running 24/7 operations can be a major issue as hard disks in close proximity to each other can accelerate hardware failures and errors. The DC HC570 counters this with a set of well-established technologies including top and bottom attached spindle motors.
WD’s standard rotational vibration safeguard (RVS) technology uses sensors placed on the edges of the hard disk’s circuit board to detect vibration ‘ripples’. The sensors signal this to the drive’s actuator allowing it to compensate by precisely controlling the head position to effectively counter the vibration and stabilize the head position.
OptiNAND and ArmorCache
Combining these technological attributes with WD’s OptiNAND shows clear advantages over the competition. WD only needed to move up to 10 platters and 20 read/write heads for its 22TB drives – Seagate and Toshiba had to implement this number for their respective lower capacity 20TB IronWolf Pro, Exos X20, and MG10 models
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. Quite simply, OptiNAND stores operational and housekeeping metadata – previously much of this had to be stored on the platters.
This isn’t 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.
Another benefit of OptiNAND is WD’s new ArmorCache technology which is a feature present in all of its 22TB drives. To achieve the best write performance, hard disks cache data in DRAM prior to writing it to the physical media but as DRAM is volatile, data that has not yet been written to the media will be lost in an EPO (emergency power off) event.
The WCD (write cache disabled) mode ensures DRAM data integrity as the drive will only cache data that it knows it can successfully write to the media. No data loss occurs in an EPO but the downside is reduced write performance.
ArmorCache gives you the best of both worlds as it uses the larger OptiNAND cache to team up the performance of WCE with the data protection of WCD. Put simply, ArmorCache allows you to choose your preferred cache mode without incurring any performance degradation or risk of data loss in an EPO.
DC HC570 Lab test setup
The UltraStar DC HC570 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.
Qnap’s TVS-882BR high-end SMB appliance with ATTO’s Celerity quad-port 16Gbps Fibre Channel HBAs were used in the appliance and host server for our high-performance tests of WD’s DC HC570 22TB hard disks
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 22TB DC HC570 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.
Performance analysis
Testing the UltraStar DC HC570 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 the same lab environment and RAID configuration used to test the 20TB WD DC HC560 and 18TB data center drives from Seagate and Toshiba so we could directly compare performance results.
WD claims a maximum sustained single-drive transfer rate of 291MB/sec for the DC HC570 which is notably higher than the 269MB/sec quoted for the DC HC560. These numbers are also an improvement over Seagate’s Exos X18 and Toshiba’s MG09 18TB which quote 270MB/sec and 281MB/sec respectively.
During testing, the DC HC570 delivered excellent performance results that matched or exceeded the competition. In our Iometer sequential read and write tests, the DC HC570 delivered impressive speeds of 3,152MB/sec and 3,150MB/sec which is close to the limit you’ll see from a 32Gbps FC connection.
For random read performance, the DC HC570 easily matched the rest with a speed of 3,152MB/sec – the same as its sequential read results. Our 100% random write test is a worst-case scenario as few businesses will have these kinds of workloads but we found the DC HC570 returned very similar results to the rest.
Differences were more noticeable when we swapped to Iometer 4KB block sizes to test I/O throughput. As shown in our graph, the DC HC570 delivered superior sequential read and write plus random read throughputs with random write speeds very slightly better.
Conclusion
Its launch of an entire range of 22TB drives covering all market sectors has put WD in a very strong position in the storage industry as no other manufacturer can currently match this feat. Even more impressive is the fact that WD’s constant innovation has shown there’s plenty of life left in standard CMR technology with the company indicating that its ePMR and OptiNAND technologies could be used to build HDDs with up to 30TB capacities before it has to move to HAMR (heat-assisted magnetic recording)
As the first 22TB CMR data center hard disk, the UltraStar DC HC570 sets a high standard for the rest to follow. It delivers a range of innovative technologies with the new ArmorCache feature offering the same performance and data protection across WCE and WCD modes
Our lab tests show the DC HC570 delivers excellent real-world performance with high IOPS throughputs. The drive is backed up by the same 2.5M hour MTBF plus 550TB yearly workload rating as the competition and also comes with a standard 5-year limited warranty.
Western Digital’s UltraStar DC HC570 is a great choice for data centers and cloud providers that want more storage in the same footprint and with unit costs currently around $545, it’s a very affordable high-capacity option.
