Pairing Solid State Memory With Traditional Storage for the Best of Both Worlds

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There is no question that, in our fast-paced world, speedy performance has become something we seek and embrace. This ever-growing need for speed explains the computer market’s increasing adoption of solid state drives (SSD), which enable streamlined performance and rapid access to data files using NAND flash memory. Yet traditional hard disk drives (HDD) remain competitive in the storage marketplace due to the lower costs and higher-capacity options they provide to computer users and manufacturers. According to recent forecasts from IDC, the HDD industry will experience a compound annual growth rate (CAGR) of 9.6% between 2011 and 2016.1

With the emergence of solid state hybrid drives (SSHD), end users and OEMs no longer have to settle for the benefits of one technology over the other. SSHDs unite SSD performance and HDD capacity in a single device. Using advanced algorithms to ensure optimal use of each technology, SSHDs offer the best of both worlds.

All of the Advantages, Without the Restraints

On their own, SSD and HDD technologies each have distinct advantages. The fundamental idea behind SSHD innovation involves joining these technologies in a way that draws on the strengths of each.

SSDs most commonly implemented in today’s computer applications utilize a type of NAND flash memory that is prone to wear from write-erase duty cycles. While data can be written to an HDD hundreds of thousands of times without wear to the device, NAND flash can only withstand approximately 10,000 to 60,000 writes, a number that varies depending on the type of flash memory used.

This wear-related issue for SSDs becomes a problem in terms of long-term durability and data integrity, particularly for business users. That is, during the normal course of a business day, users with SSD-equipped laptops unknowingly shorten the working life of the SSD’s flash memory by performing typical job tasks that are write-erase intensive, such as creating and revising a document.

On the HDD side, the mechanical components within HDDs are also subject to wear and tear over time and are more prone to shock-related damage compared to SSDs. Hard drive bearings are constantly in use when the motor is spinning, even if the rest of the device is idle. Additionally, contact between the actuator head and the media platter during reads can cause further wear.

So how do Seagate® SSHDs achieve maximized performance and reliability from both technologies? The answer to this question is Adaptive Memory™ technology. In order to make the most efficient use of both the flash memory and HDD storage on their SSHD products, Seagate developed an advanced set of algorithms to track data usage and intelligently determine which data should be stored in the flash memory portion of the device. These algorithms revise the allocation of data as usage priorities change over time.

Combining HDD media and a small amount of NAND flash memory (along with Adaptive Memory technology) into a single device, SSHDs offer a particularly synergistic use of both storage technologies. SSHDs overcome the inherent weaknesses of SSD and HDD technologies by writing primarily to the hard drive media and reading primarily from the NAND flash.

By directing the majority of writes to the HDD portion of the device, SSHDs limit write-instances to the NAND flash memory, therefore extending the working life of the solid state component and improving its overall reliability. Similarly, reading from the NAND flash part of the SSHD allows the HDD media to spin less, reducing wear on the mechanical parts and minimizing opportunities for head/media contact within the drive.

A Breakthrough for Storage Reliability

Because of the ways that NAND flash and HDD media complement one another, Seagate expects SSHDs will surpass separate SSD and hard drive technologies in terms of reliability. This expectation is supported by recent field reliability data. The graph below displays field return data from a single Seagate customer shipping multiple notebook class products. This information displays cumulative return rates over an average six-month window.


As evidenced by the data, second-generation Seagate SSHD products (SSHD P2) achieve the lowest field return rates of all laptop products shipped. The data also indicates that the SSHD product demonstrated higher reliability in the field than the base HDD program on which it was designed (HDD P2).


The days of choosing between SSD performance and HDD capacity are gone. SSHD solutions join the best features of the two technologies, creating an ideal unification of performance, capacity and reliability. With intelligent algorithms to analyze and direct data, SSHD devices enable the most appropriate use of both NAND flash memory and hard drive media for today’s computer workloads. In the world of computer storage, SSHDs are making it possible for users to have it all.

1IDC, Worldwide Hard Disk Drive 2012-2016 Forecast: The Industry Hits the Rest Button, IDC #233547, Volume 1, March 2012.

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