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Flexing SSD Strengths for High-Reliability Data Recorders
Taking SSD Technology to the Next Level
SSDs commonly use two types of memory: DRAM and flash. DRAM-based SSDs are based on volatile memory components and need some data retention mechanism (built-in batteries, non-volatile mechanical backup such as rotational HDDs) when the power supply is removed.
On the other hand, flash memory-based SSDs make use of non-volatile memory chips. If power is lost, the drive can preserve acquired data in excess of ten years even in extreme temperature changes without the need for additional backup components. This inherent non-volatility of flash SSDs not only means safer data but also makes them much lighter, smaller and quieter than DRAM SSDs. This is ideal for embedded data recording applications that often have limited capacity for space and power. Table 2 compares the physical aspects of a SCSI Wide DRAM-SSD from Curtis, Inc., to a SCSI Wide Flash-SSD from BiTMICRO.
|
SCSI Wide DRAM-SD |
SCSI Wide Flash-SSD |
Form Factor |
3.5 inch |
3.5 inch |
Maximum Capacity |
12 GB |
147 GB |
Maximum Weight |
2 lbs (0.17 lbs per GB) |
2.35 lbs (0.015 lbs per GB) |
Power Consumption |
6 watts |
= 4.5 watts |
Table 2: Curtis Nitro!XE vs. E-Disk Ultra Wide SCSI
Source: Curtis website (05/05/04) and BiTMICRO website (09/10/2004)
The volatile nature of DRAM suggests that in order for DRAM SSDs to ensure data preservation even in the absence of power, additional components such as backup batteries and hard disk drives are required. However, the mechanical nature of such devices makes them prone to damages from shock, vibration and extreme temperatures. Flash SSDs do not have mechanical parts, allowing them to withstand tremendous shock and temperature extremes without affecting operation or reliability of the data. Table 3 compares the operating characteristics of the Curtis SCSI Wide DRAM-SSD to a BiTMICRO SCSI Wide Flash-SSD.
Every storage device also needs some level of error checking to ensure data integrity. This is critical to any data recording application because it would be very costly, if not catastrophic in some applications, to have incorrect or corrupted data. Some SSDs implement a proprietary application of the Reed-Solomon Error Correction Circuitry (RS-ECC) specifically designed for flash memories with a bit error rate of 10-20. This order of magnitude difference means that for every 512-byte block, nine byte errors can be detected, and six byte errors can be corrected. The best that other storage devices can do is to detect only three byte errors, and properly correct it only 20 percent of the time.
|
SCSI Wide DRAM-SSD |
SCSI Wide Flash-SSD |
Operating Temperature (max) |
5°C to 45°C |
-60°C to 95°C |
Humidity |
10% to 90% non-condensing |
5% to 95% non-condensing |
Altitude |
10,000 feet |
-1,200 to 120,000 feet |
Table 3: Curtis Nitro!XE vs. E-Disk Ultra Wide SCSI
Source: Curtis website (05/05/04) and BiTMICRO website (09/10/2004)
Security and Ease of Use
Some data recorders, especially military, capture highly sensitive data. Unmanned aerial vehicles (Figure 1), fighter planes and tanks in enemy territory run the risk of capture and therefore put their sensitive data at risk. This makes data security a high priority in these types of applications. SSD manufacturer, BiTMICRO Networks, offers a technology that allows users to irretrievably destroy stored memory on demand or automatically, even in the absence of an external power source, in compliance with the remanence security requirements of the DoD, NSA, Air Force, Army and Navy.
Ease of deployment is another consideration when it comes to using new technologies in traditional applications. Data recorders have long been using magnetic media; thus, incorporation of newer technologies should be simple. Flash SSDs come in the same form-factors as HDDs and support the most common interfaces. They are plug-and-play compatible with HDDs and are easily deployable in applications that use disk arrays or disk groups.
Data recorders are often deployed in unmanned aerial vehicles such as Global Hawk
Flash SSDs bring other benefits as well. Users can save money, since flash SSDs are reusable. Faster sustained writes allow flash SSDs to take twice as many shots. There is no gap between reloads, so planes don't have to fly around twice. When recorded images are viewed for evaluation, multiple users can look at different frames simultaneously (no rewinding). Flash SSD solutions are lightweight, ruggedized and can survive high altitudes and varying temperatures.
With the ever-increasing demand for more reliable and higher-resolution data collection, SSDs are now becoming the storage of choice for data recorder professionals. With its advanced data protection technology and extremely low bit error rates, the integrity of stored data in flash SSDs is ensured even in the most critical of applications. Rapidly declining prices and improved production efficiencies have made flash memory nearly ubiquitous in digital consumer electronics. As manufacturers realize the huge price/performance benefits of flash SSDs, solid-state flash storage will steamroll into enterprise, military and industrial applications, and data recorders will never be the same again.
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