TECHNOLOGY IN CONTEXT
Solid State Storage
“SWaP” the HDD Form-Factor SSDs in Embedded System Design
The solid state storage solutions now available enable industrial and embedded system engineers to optimize the size, weight and power of their latest designs, breaking the mold of old rotating media form factors.
ADRIAN R M PROCTOR, VIKING MODULAR SOLUTIONS
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In today’s platforms, embedded and industrial rugged system designers continue to search for better ways to deliver solutions with optimal SWaP (Size, Weight and Power) characteristics. These are critical for improving operational life, reliability, mobility and cost. The term “SWaP” was first coined by the military, who needed to create small, lightweight and rugged systems solutions, yet a new breed of embedded and industrial designs are now investing in the technologies required to minimize the footprint of their equipment. Nearly all of the components used in high-performance system design have been optimized in some way, i.e. smaller, faster or more dense, proving Moore’s Law. The law, named for Intel co-founder Gordon E. Moore, posits that the number of transistors that can be placed on an integrated circuit board doubles approximately every two years, and the theories behind this idea have helped to push along the developments in processor and memory technology at a healthy clip.
There has been a notable exception to this rule—the physical size and weight of the storage component of system design. For years the governing bodies that create industry standards for storage have been focused on supporting Hard Disk Drives (HDD) that meet the industry standard 3.5”, 2.5” or 1.8” form factors. What has evolved is higher-performing, more robust and higher-capacity storage, but no great innovative leaps to deliver all of this in a reduced size.
However, with the widespread adoption of Solid State Drives (SSDs) in a multitude of embedded and industrial applications, these SSDs have offered not only the “W” (Weight) and “P” (Power) benefits of SWaP over HDDs, but also significantly higher levels of Reliability, Availability and Service (RAS)—all highly desirable features for mission-critical commercial applications, especially those in rugged or mobile environments.
But what about the “S” in SWaP, namely “Size”?
There are a number of these BGA solderable “chip-sized” SSDs available in the market (Figure 1), but they will typically only deliver up to 4, 8 or 16 Gbyte of SATA/PATA storage at relatively low levels of performance (enough for OS/Boot or storing code). These single-chip SSDs do provide low density support for space constrained and rugged environments (Figure 2), yet they fall significantly short of the mark when requiring high performance (100 Mbyte/s+) or high capacity (100 Gbyte+) for the application.
Chip-sized, solderable solid state drive.
Chip-sized solid state drive on single board computer.
There is no physical reason why Solid State Drives (SSDs) should be inhibited by the HDD form factor constraints. Unlike traditional hard disks, SSDs do not rotate a platter or require mechanical housings, yet the additional weight of these metal housings are added to embedded rugged applications unnecessarily. Additionally, the infrastructure that has historically supported HDDs (rails, brackets, etc.) was designed to reduce vibration, something that an SSD will not require, yet the weight of all this metal remains in place purely because the standard 3.5”, 2.5” or 1.8” infrastructure demands it (Figure 3).
A hard disk drive’s housing infrastructure is not needed for solid state drives.
While a standard 2.5” form factor SSD will deliver a far reduced weight and power solution when compared to an equivalent HDD, there is still significant room for improvement. The unnecessary metal used in standard SSD integration can easily be removed by using some of the newer and more innovative “Non-HDD-like” SSD solutions available in the market today. These “SWaP optimized” SSDs can take the form of a DIMM, volumetrically efficient Cube design, reduced size, or simply a case-less standard form factor SSDs.
System designers can free up their valuable board space with these “SWaP-friendly” SSD solutions while achieving the data reliability, rugged requirements, performance and capacity needs that the embedded, industrial, rugged and military markets demand.
The current crop of AdvancedTCA, MicroTCA, cPCI, AMC and other embedded products are available as multicore, high-performance solutions that deliver the processing punch demanded by many of today’s embedded applications, yet the rugged storage component is typically located in other areas of the system or takes up a whole card (Figures 4 and 5). These small form factor processing cards will host the CPU and main memory (in some cases with multiple DRAM module sockets), yet rarely have any more storage than that of a “chip-sized” device—until today.
For example, an Advanced Mezzanine Card (AMC) will house a single 2.5” HDD or SSD for storage, yet by using a Slim SATA SSD (a form factor ratified by JEDEC as MO-297), the system designer can fit multiple SSDs on the AMC card enabling aggregated bandwidth / performance, RAID capabilities, increased redundancy or simply save space for other components or features on the card.
Looking further at the space efficiency of some of these unique, volumetrically optimized SSD solutions, a SATA Cube (Figure 6) can provide the same storage capacity as a 2.5” SSD in 1/6th of the area, but perhaps more importantly; this solution can deliver six times more capacity and performance in the same physical area. This means that the embedded system designer can deliver either high-capacity storage, high-performance storage or ultra-compact storage; something that will surely provide a high degree of value to the end user. This Cube SSD, like the “chip-sized” SSDs, has a solderable interconnect for increased levels of ruggedness; environments where this would be useful include vehicle-based systems or black box / event recorders.
This SATA Cube offers six times more capacity or performance in the same space as a 2.5” SSD.
There are of course many hundreds of applications that are severely size and weight limited, and the primary design considerations are typically those of SWaP. Even in the large mechanized world of rail transportation infrastructure companies today are rapidly adopting high-tech solutions to help them manage and maintain their transportation fleet. Embedded systems designers are able to deliver rugged, high-performance and high-capacity event data recording equipment that is able to record the data that is essential for operating and maintaining safe and efficient vehicles.
These data recorders, often utilizing small form factor, rugged SSDs, provide vital and valuable information for accident investigations, train handling studies, fuel conservation, vehicle performance and preventative maintenance programs.
There is considerable evidence that the continued investment in R&D has clearly allowed the embedded design world to focus on wide scale miniaturization and certain technologies that have been driving SWaP reduction. However, in the case of the SSDs highlighted in this article, the industrial embedded system designer can breathe life into their new designs with the confidence that these solutions deliver a balance between SWaP and price. Moreover, they will deliver a higher degree of performance and capabilities, something that is sure to set them apart from their competition.
The bottom line is that design engineers no longer have to be constrained by HDD storage standards. These engineers are now free to explore creative 3-D designs that have been limited by the old standards originally developed for rotating media. Additionally, these “SWaP-optimized” SSD storage solutions can give rise to new ways of managing challenges in the increasingly difficult areas of thermal efficiency, vibration, shock resistance and efficient use of space management.
Viking Modular Solutions
Foothill Ranch, CA.