New Areal Density Point for Cloud Storage HDDs


Seagate has announced a 6 TB hard disk drive for data center applications.  While other companies, such as Western Digital ‘s HGST division have announced 6 TB drives using He-filled drives with additional disks, the Seagate drive represents roughly a 25% areal density increase (the amount of digital storage that can be stored on a unit area of the disk surface).

The Seagate Enterprise Capacity 3.5 HDD v4 is available with a 12 Gbps SAS or 6 Gbps SATA interface and is said to deliver up to a 25% increase in performance over competing 6 TB drives.  The drive family also includes self encrypting drive (SED) technology for rapid cryptoerase with no cost penalty versus a non-encrypted drive.  In addition the drive offers 4 k native sectors unlike past drives, allowing for a higher format efficiency, and thus additional user accessible data.

The 6 disk drive increase the disk capacity from prior generation 800 GB per disk to 1,000 GB (1 TB) per disk, representing a 25% increase in capacity per disk and thus in areal density.  Apparently this is done without resorting to Shingled Magnetic Recording (SMR) and thus represents a significant increase in general drive areal density while allowing direct overwrite of data and avoiding the additional overwrite overhead of SMR drives.  This announcement pushes the areal density of shipping HDDs close to 1 Tbpsi (terabit per square inch).

While He in a drive can allow more disks in a drive with other advantages on power consumption, heat generation and higher capacity the costs will be higher with the extra disks and with the hermetic sealing of the drive vs. a conventional drive with higher areal density.  Likewise a hard disk drive with increased areal density will have performance benefits compared to a drive using SMR technology, especially for overwriting prior data.

By my record this is the first increase in drive areal density since a 7% increase in Q2 2013.   The increase in Q2 2013 was the first one since Q3 2011.  The rate of increase in HDD areal density has slowed down considerably since the start of this decade, giving technologies like flash memory a basis for claiming that  they will catch up to the price of HDD capacity in $/GB.  The increase reported in the Seagate announcement, if propagated across their product lines, will support the continued cost effectiveness of hard disk drives vs. solid-state storage.

We are expected that 10 TB drives or larger will be available in the next couple of years as various technologies are implemented in HDDs to increase the storage capacity of the drives. This will help cloud storage and data center companies that are dealing with increasing content in near line storage applications. Although the role of HDDs in the highest performing enterprise applications is likely on the wane it appears that HDDs will continue to provide a good value for higher latency data storage, supporting many hyperscale storage requirements.

By Jarrett Neil Ridlinghafer 
CTO of the following –
Synapse Synergy Group
Chief Technology Analyst, Author & Consultant
Compass Solutions, LLC
Hadoop Magazine
Cloud Consulting International