Date: Wednesday, April 10, 2013
Seagate has made the bold move of terminating its entire line of 2.5" 7,200 RPM performance HDDs in favor of its new line of hybrid hard disk drives. Seagate has opted to market these hybrids as SSHD (Solid State Hybrid Drives), and jettisoned the previous Momentus XT branding. Regardless of branding, Seagate has tremendous faith in this new technology, essentially going 'all-in' on SSHD.
2.5" 7,200RPM HDDs were always a niche market typically deployed into high-performance laptops. This market segment has been under a continuing assault by SSDs, and abandoning that product category will require a replacement that is comparable in capacity, performance and price to the previous HDDs.
The new SSHD will come in two distinct categories with different models for both the desktop and laptop. The 2.5" models are headed into laptops under the Laptop SSHD and Laptop Thin SSHD monikers. These 5400RPM mobile HDDs will have two capacities and Z-Heights. The Laptop SSHD features 1TB of data held on two platters with a thickness of 9.5mm for higher capacity in full size laptops and retails for $79. The Laptop Thin SSHD has 500GB of capacity on a single platter in a package 7.0 mm thick to achieve maximum density in Ultrabook and other slim applications for $99.
The choice to go with a 5,400RPM design is largely due to power constraints in mobile applications. The combination of Windows 8 and the Ultrabook initiative has tightened the operating envelopes for integrated storage solutions drastically in terms of both power and performance.
Desktop SSHD's will consist of a standard 3.5" form factor in capacities of 1TB and 2TB, for $99 and $149 respectively, and retain the original 7,200RPM speed.
SSHDs function by using a small buffer of NAND to store frequently accessed hot data. When radically accelerated this hot data can significantly alter the entire computing experience. Perhaps the most interesting aspect of NAND accelerated HDDs is the small percentage of cached data required to facilitate dramatic application acceleration.
We have conducted extensive testing of stand-alone SSDs that can accelerate existing HDDs in conjunction with software caching algorithms. This type of solution is becoming increasingly popular and we evaluated two of the best solutions currently available, the Corsair Accelerator 30 & 60GB and the SanDisk ReadyCache 32GB SSD. These are full-size SSDs that slip in and provide massive acceleration to the overall computing experience; and with as little as 30GB of NAND can accelerate even large 3TB volumes.
The Seagate SSHDs only have 8GB of NAND yet still provide tremendous acceleration with this limited amount of space. To provide an example Seagate organized an internal study of its own employee's data usage patterns. Over a five day period the average amount of data read by the employees was 19.48GB, and only 9.59GB of that data was "unique" reads. The remainder of the data read was simply duplicate reads. Using its Adaptive Memory Technology, Seagate was able to accelerate 95% of the workloads to the speed of a full SSD install, with only 2.11 GB of the data stored in cache.
The key is to intelligently assess the data and act accordingly. The Adaptive Memory Technology algorithms utilized to manage the NAND have matured significantly. With this third generation SSHD product the enhanced NAND management led to a switch from SLC to MLC NAND. Seagate has also found a method to leverage enhanced cache tiering in the small amount of available cache, and we will cover this approach on the following page.
This helps to significantly reduce the cost of the solution, feeding the dual need of competing with SSDs and at the same time competing with higher RPM HDDs. If priced too high customers will either opt for the much cheaper HDD, or go with the only slightly more expensive SSD. Finding that middle ground to stave off both competing markets is the key to success, especially when taking into consideration that Seagate has abandoned the high performance 2.5" HDD market entirely in favor of these 5,400RPM SSHDs.
Today we will put the drive to the test in comparison to software caching SSD solutions and a typical 7,200RPM HDD to see if the move pays off.