Western Digital introduces new non-SMR 20TB HDDs with onboard NAND

This isn't Western Digital's first 20TB drive—but it is the first shipping drive to achieve that density without the use of Shingled Magnetic Recording (SMR) technology.

Enlarge / This isn't Western Digital's first 20TB drive—but it is the first shipping drive to achieve that density without the use of Shingled Magnetic Recording (SMR) technology. (credit: Western Digital)

At Western Digital's HDD Reimagine Event yesterday, the company introduced its newest hard drive architecture—a hybrid spinning rust/NAND flash design it calls OptiNAND. But as WD President of Technology and Strategy Dr. Siva Sivaram told Ars in an interview, OptiNAND bears almost no resemblance to the much-maligned hybrid SSHD drives first introduced in 2011 and 2012.

Instead of promising SSD-like speeds via caching of customer data, OptiNAND offers increased areal density by removing firmware-accessible metadata from the disk itself and storing it on NAND instead.

20TB per disk without SMR

Like last year's 20TB SMR drives, the OptiNAND drives employ EAMR in the form of an additional current to the main pole of the write head. [credit: Western Digital ]

The most tangible milestone achieved by Western Digital's newly announced architecture is a nine-platter, 20TB drive that does not require Shingled Magnetic Recording (SMR) techniques. The new disk uses a subset of Western Digital's EAMR technology, which has been rebranded ePMR—presumably to emphasize that it's not SMR, which has severe performance and usability implications for many common workloads.

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