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WD Launches Dual-Actuator 20TB HDDs With SATA SSD-Like Throughput
In a rather unexpected move, Western Digital introduced its first dual actuator hard disk drives (HDDs) on Monday, matching its competitor Seagate's impressive Exos drives that use similar tech. The dual actuator Ultrastar DC HS760 20TB HDD builds upon the proven single-actuator Ultrastar DC HC560 drive, but doubles its sequential read/write speeds to the types of speeds we see with SATA SSDs and also nearly doubles its random read/write performance. The key advantage of the new HDD for hyperscale cloud data centers is increased IOPS per terabyte.
Two independent actuators in the drive work in parallel, offering up twice the sequential throughput (up to 582 MB/s), which is on par with a SATA SSD in throughput, and 1.7X higher random performance than a single-actuator HDD (still not comparable to an SSD). WD also claims the drive consumes up to 37% less power than two separate hard drives. For some reason, Western Digital did not publish detailed specifications of the product, though we hope to see a datasheet soon.
The Ultrastar DC HS760 20TB dual actuator hard drive uses Western Digital's third generation OptiNAND platform, featuring nine 2.2TB ePMR (energy-assisted perpendicular magnetic recording technology) platters and NAND flash cache to store metadata and write cache data to boost performance and increase areal density.
The Ultrastar DC HS760 drive is accessed via single-port SAS and presents itself as two 10TB logical unit number (LUN) SAS devices. Since the logical HDDs are independently addressable, they need software tweaks on the host side. To that end, not all data centers can use the new drive.
Western Digital's Ultrastar DC HS760 20TB HDD offers higher capacity than Seagate's dual-actuator Exos 2X18 18TB hard drives, but Seagate also offers its drives with a SATA interface, which makes it compatible with a wider range of customers.
As the capacity of HDDs increases, their IOPS-per-TB random read/write performance drops, which makes it harder for data centers to maintain their quality of service. Dual-actuator HDDs solve this problem by significantly increasing the performance of HDDs, albeit at the cost of somewhat higher power consumption.
Like other Western Digital Ultrastar drives, the DC HS760 20TB has a five-year warranty and is intended to work in 24/7 environments. Each LUN is designed to handle up to 500TB per year, slightly lower than the 550TB-per-year workload of typical data center HDDs.
Western Digital does not disclose the pricing of its dual actuator HDDs, but they will naturally be more expensive than single-actuator hard drives. Also, since these storage devices are designed for data centers, their actual price will depend on many factors, such as volume and established or new long-term agreements.
