iSLC Flash Technology

December 1, 2013

Robots have been employed by the military to assist in missions where it would be, and has been, too dangerous to have a human being take on the task. These robots can detect and disable bombs. Some can be thrown into rooms where they land on their “feet”, and scan the room for counter-insurgents. Others blow up mine fields, to ensure safe travel of ground vehicles and the personnel they carry.

Ground vehicles have benefited from technology advancements as well. Some MRAP vehicles hold several satellite dishes that relay data from their location. MRAP vehicles are being equipped with multi-band radio systems that can relay sensitive data via tactical satellites from their location. They can track movement and sense projectiles being launched from many angles.

Manufacturers and designers have made significant strides over the last decade; one can only imagine what warfare will look like in the next ten years.

Military Electronics

The military electronics industry is going through drastic change as defense budget cuts create a need for military compliant storage solutions that are cost-effective without sacrificing performance or the reliability required for mission-critical military applications.

Traditional hard drives may have their advantages (cost and capacity), but they are lacking in performance (65- 85MB/sec) and flexibility of size, they generate more heat (up to 10W), and they are not equipped to withstand shock and vibration. Advances in alternate technologies can have a significant impact on the abilities of a robot or vehicle.

NAND Flash Overview

Designers of automatons, ground vehicles, and UAV’s are turning to flash storage devices to store data and run onboard systems.

Flash storage devices contain various grades of NAND (negated AND) flash architectures, or cells that are used to store an electronic charge . The quality of the NAND flash can affect the speed and number of performance/endurance cycles the drive has in its lifetime. The benefits to using flash storage are its size (multiple form factors), speed, reliability, vibration and shock tolerance, and low power consumption (less than 1W).

For mission-critical applications, the United States military has been partial to devices that contain SLC NAND flash, or single-level cell flash architecture. SLC flash technology stores one bit of data in a single cell, in two states: 0 or 1. It is widely known as the most reliable architecture, with 100,000 P/E cycles. Additionally, SLC-based flash generates fewer errors per write cycle, allowing it to bypass the robust degree of error correction required for MLC. The downside is that the price-tag for products with SLC NAND flash is significant enough to put a dent in anyone’s budget.

For years, the cheaper alternative was to use MLC flash-based products. MLC NAND flash, or multi-level cell flash architecture, stores two bits of data in a single cell, in four states. These four states are as follows: 00, 01, 10, and 11. This allows for higher capacities at a lower price point, but it is not a preferred solution for applications where failure is not an option. MLC flash requires a more robust ECC engine as MLC-based flash generates many more errors per write cycle.

iSLC NAND Flash

iSLC NAND flash architecture was developed as a hybrid solution for those that require high-performance at a lower price point. iSLC enhances superior MLC through screening and programming by patented firmware. The MLC flash is preprogrammed into one bit per cell, which increases the sensitivity of delta between each level. This practice enables the NAND flash to perform similar to an SLC flash based solution.

iSLC is designed to overcome the inherent deficiency in MLC NAND flash due to ever increasing demands on performance and endurance. With iSLC technology, a 32GB capacity drive can sustain ten full disk writes a day for over seven years (Figure 1).

iSLC offers an improvement over the endurance of MLC to further suit the needs of industrial SSD applications. iSLC increases SSD lifespan by ten times, mimicking the performance of SLC flash.

Specially designed, in-house firmware forces the MLC flash to act as SLC flash. Each SLC cell holds one bit – 1 or 0 – while MLC holds 2 bits – 00, 01, 10, 11. iSLC mimics SLC by only holding one bit in each NAND cell. This firmware also increases endurance and data retention levels of the MLC NAND Flash (Figure 2).

Military Standards: Flash Storage Devices

There are always challenges when implementing new technologies. The military has strict guidelines when it comes to operating temperatures and materials testing specifications in extreme environments (MIL-STD-810F/G). Many of the drives that the military uses for their most mission-critical applications adhere to MIL-STD-810F/G, especially those that operate in temperatures between - 40°C ~ +85°C.

While iSLC is being tested to comply with the above MIL Spec, devices with iSLC can already be employed in instances where the mission is critical, but the environments are not as extreme as described in the MIL Spec. “Throwbots” and five-pound rovers could benefit from a cost-effective technology that is highly reliable, can be easily replaced, and has high performance standards.

Flash devices come in many form-factors, including 2.5" SSD, 1.8" SSD, CF, CFast, and the latest SATADOM form factor, which is shorter than a one dollar coin. Many come with or without housing, depending on the engineer’s needs. Innodisk has the added benefit of the ability to create in-house firmware that can be customized to any system. Projects can have a myriad of requirements, from faster boot-up times, and longer hardware testing time, to high IOPS, and sequential performance requirements. Products can also be customized for the extremes: high temperatures, hostile environments, high altitudes, and sea submersion.

The Next Generation of Systems

The US Defense Budget for FY2014 is estimated at $615.1 billion dollars , with an estimated $67 million dedicated to Research, Development, Test & Evaluations. The word “unmanned” appears nine times in the RDT&E Programs Budget, and is in reference to aerial and ground vehicles. Engineers and researchers are constantly trying to develop the next robot or vehicle that will protect soldiers in battle. These robots and vehicles are only as good as the sum of their parts. It takes next-gen components, like highly developed flash storage devices, to make a product that can act, without failure, at a crucial moment on the battlefield.

This article was written by Edwin Lam, Senior FA Engineer, and Jessika Remolona, Marketing Specialist, Innodisk (New Taipei City, Taiwan). For more information, Click Here .

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