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By Rudy Bruce, BiTMICRO Networks

Data acquisition and recording technology has grown exponentially over the past years as data recorder manufacturers try to keep up with faster data gathering speeds and more precise measurements. Data recording for military and civilian applications is a major issue, since it could spell the success or failure of operations or, in worst-case scenarios such as the battlefield, the life or death of individuals.

One case that comes into mind is the deployment of Spirit and Opportunity, NASA's twin Mars Exploration Rovers. Equipped with a variety of spectrometers, cameras and other tools, their primary mission is to search for answers about the history of water on Mars. Data recording and transmission is an essential aspect of this mission, and failure to record/store data would mean billions of dollars and several years of research down the drain.

Another concrete example is the flight data recorder (popularly known as a "black box") installed in civilian and military aircraft. Implementation of stricter safety requirements for commercial airlines has led to the development of data recorder solutions that can gather more parameters with greater accuracy. More parameters mean less other resources are required to finish a crash investigation.

Aside from these cases, there are many circumstances in which data collection and recording is just a one-time opportunity, making it necessary to deploy reliable data recording equipment and a storage subsystem that can keep up with input coming from high-speed sensors. This article discusses the feasibility of using solid-state flash disks as storage media for these data recorders, both from performance as well as cost standpoints.

Issues with Legacy Data Recorders

Mass storage has undergone several transformations ever since the introduction of punch cards during the mid-1800s. The 1940s saw the introduction of vacuum tubes for storage, while tape drives began to make their presence felt in the early 1950s. A couple of years later, magnetic drums were introduced and, in 1957, IBM rolled out the first rotational hard disk drive (HDD).

Tape drives and HDDs have survived the onslaught of silicon-based storage devices and are still available in the market. However, even though these storage media are widely utilized in business enterprises, they have weak points that can make them susceptible to failure under certain data recording applications.

While the magnetic tape drive has been a mainstay in the data recorder industry, this storage solution has inherent weaknesses:

• Data retrieval is slow due to sequential access: To retrieve a file, it's necessary to start at the beginning of the tape and move forward until the file is located. This process of rotating the tape media back and forth over the drive head can disrupt the playback of non-sequential data segments.
• Susceptibility to damage: Tapes must be stored in climate-controlled locations, since they are highly susceptible to damage by humidity, dust, heat, light and magnetic fields.
• Storage space required: The size of the magnetic tape is so big that its storage space becomes bulky.
• Quality of recording degrades over time: The quality of magnetic tapes eventually degrades over time, affecting recorded data.
  
  

Magnetic disk drives, more popularly known as hard disk drives (HDDs), have solved performance and durability issues associated with tape drives. However, HDDs are not without their disadvantages. As files are written onto and deleted from a HDD, data fragmentation occurs. Fragmentation has a negative impact on performance, since disk heads require additional time to move around to various points on the disk to read scattered file parts, resulting in a gradual deterioration of system performance-longer reads and extended reboots. In addition, HDDs contain mechanical components such as the read/write heads and spindle motors which, when subjected to shock and vibration, may damage the hard disk platters, resulting in bad sectors.

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