HDD Capacity Threshold Reaches 15TB

HDD Capacity Threshold Reaches 15TB

Chris EvansPodcast, Storage Hardware, Storage Media

Western Digital has announced what is currently the largest capacity hard drive available on the market today – a 15TB HDD.  The Ultrastar DC HC620 has 15TB of capacity in a helium-filled 3.5″ form-factor.  This is a 7% increase (or obviously 1TB) over the 14TB drive announced in October 2017.


The new capacity drive looks more like an incremental change than anything radically new.  HS14 drives are helium-filled and use SMR (Shingled Magnetic Recording) to increase the areal density on each platter.  We can expect to see these drives being used in edge scenarios like video recording systems, where the profile of access is mainly sequential writes.

The HC620 has one important feature to note.  This is a “host-managed” SMR drive, meaning that the connected host, rather than the drive is responsible for managing the sequential zones that make up the SMR media.  Shingled Magnetic Recording uses a technique that overlaps tracks, requiring data to be written sequentially.  This process can be managed by the drive itself or by the host.  Drive-managed SMR can result in poor write performance, so allowing the host to optimise writes – especially in scenarios where the data isn’t randomly accessed – can offer much greater performance.

We discussed the idea of hyper-scalers wanting more control over drive hardware in a Storage Unpacked podcast with SNIA’s Mark Carlson earlier this year.

Western Digital points to Dropbox as one customer implementing host-managed drives.  You can find out more on this Dropbox blog post and more about Magic Pocket in the Tech Field Day video embedded below.

Dropbox Background on Magic Pocket with James Cowling from Stephen Foskett on Vimeo.

The Architect’s View

We’ve talked before about storage for hyper-scalers and evolving some of the functions of drives to the host.  The implementation of host-managed SMR is one example of this and I’m sure we can expect more in the future.

At a recent A3 Technology Live! event, Seagate presented their view for the future of high capacity drives.  Seagate is betting on HAMR (heat-assisted magnetic recording) and had an amazing presentation showing some of the science needed to get HAMR to work.  Once the video are available, I’ll be sure to share them online.

Despite the announcement of multi-actuator drives, the focus for the hard drive industry is on capacity.  That’s OK, because the storage industry is already diverging into many tiers of storage, of which hard drives will still form a big part.

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