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Flash storage in rugged industrial applications

Feature

By Jason Cardona, US-based technical writer

Industrial OEMs see value in optimising the right flash technology to ensure host architecture compatibility whilst meeting their workload requirements. During the design process, manufacturers of industrial products undergo long engagement processes with multiple part suppliers. This ensures that each embedded part will work for the application and that it will meet the workload and environmental requirements in the field, too.

Supplier engagements can be lengthy and complex, leading OEMs to purchasing off-the-shelf parts, particularly commodity items. Flash memory falls into this category; it’s normally selected based on type, capacity and form factor.

Because flash memory is widely available in a variety of sizes for consumer electronics, many OEMs assume they can proceed without a customised solution. However, in doing so, they may overlook considerations such as the frequency of reading and writing large amounts of data to memory; power management issues – dirty power, power cycling, power failure; and environmental conditions – temperature, vibration. These factors can lead to data corruption and other errors in the field, whilst reducing the reliability and lifespan of the flash storage. For industrial OEM products, which can have a lifecycle longer than 3-5 years (compared to 6-18 months for consumer applications), this can cause failures in the field and reduce the product’s overall life.

“Many industrial OEMs purchase flash storage devices over the Internet, only at the launch of their product to discover unexpected issues due to inaccurate assumptions about the environment and workload requirements,” says Tony Diaz, Product Manager for Delkin Devices.

Wrong application assessment can lead to severe consequences for users. In the transportation industry, for instance, the unexpected failure of mission-critical data may lead to the compromising of safety features that drivers rely upon to prevent accidents. In manufacturing automation, unexpected data device failures can cause machinery to malfunction, potentially leading to a costly and disruptive cessation of production.

Given the critical role in storing mission-critical data, Diaz says the majority of industrial flash storage solutions require some level of customisation to adequately meet workload requirements in real-world industrial scenarios.

Workload demands

All flash storage has a finite life, depending on how well it’s managed. To optimise and extend its life, careful consideration must be given to how data is written to it. Writing is the process of prepping the blocks of flash and then programming new data into them. New data can be saved to flash after first erasing the old one. Due to the nature of this type memory, only a finite number of programming and erasing cycles can be performed before it becomes unreliable. Also, some flash media is not used evenly, further reducing the life of the device.

Fortunately, there are options to extend its life, with reducing unnecessary copying of files or downloading of data, consolidating writes, wear levelling techniques and selecting whether data is written sequentially or randomly.

“If an OEM misjudges or misunderstands the workload requirements, there are implications for the storage,” explains Diaz. “It could be as simple as unexplained errors in the field, or it could be a situation where they are wearing out the flash memory much faster than they realise.”

Environmental conditions

An important flash storage customisation option involves mechanical ruggedness: Is the application subjected to unusual amounts of vibration? Does the typical operating environment exceed standard industrial storage parameters? Although industrial flash storage is designed to be rugged, different applications have different operating requirements. Customising the mechanical ruggedness of the storage can alleviate concerns about failures associated with operating conditions.

One of the best ways to ensure that a storage device will work as expected in operating conditions is to partner with a manufacturer who offers testing reliability services. Companies like Delkin Devices, for example, offer design verification testing, ongoing reliability testing and even accelerated lift testing to simulate long-term operating conditions at its manufacturing facility in San Diego, California.

Power issues

One of the more common real-world scenarios for industrial flash storage is power issues such as dirty power, excessive power cycling and unexpected power failures.

When power is lost during a write operation, it can cause data loss because the data wasn’t completely saved. Although only a small amount of data may not have been written when a power failure occurs, it can cause significant ongoing problems, including fatal corruption of the entire system. It can also cause inefficient use of memory capacity, which can dramatically shorten the lifespan of the embedded flash storage.

Taking steps to reduce external sources of power loss is important for mitigating the risk of power fails. However, power failures can still occur, so internal protections are essential for reducing the risk of data loss. For flash memory systems that handle critical data, that means built-in power loss controls, including systems for monitoring power supply and the ability to recover data after a power loss that occurs during a write operation.

Dirty power due to outages, brownouts, surges and power spikes is another concern. This can be particularly problematic in transportation where DC dips below the required threshold, which can confuse the source and lead to errors in equipment critical to the operation of trains, automobiles or airplanes.

Excessive power cycling to conserve battery life can also be a problem. In some industries where OEM products are used in remote locations, the power is cycled tens of thousands of times a year to keep the battery in sleep mode or to power it off altogether. This can also degrade the performance of the flash memory.

Delkin’s industrial-grade memory storage family

Operational issues

Finally, the operational requirements refer to the manufacturer’s supply chain and how they go about sourcing parts, engaging suppliers and ensuring that the parts they source will be available throughout the product lifecycle.

It is very common for the bill of materials (BOM) of commercial grade flash storage to be updated without warning, and this is necessary for consumer OEMs because it helps maximise functionality whilst minimising price. For industrial OEMs, however, consistency and reliability are needed above all.

Diaz says there is an even higher standard that can be achieved, which is when the component parts are controlled and “locked”. “This means that once qualified, the flash, controller and firmware will not change as long as the part number is active. If anything needs to be changed, the part number is changed, essentially guaranteeing that the customer is notified and the BOM updated,” he said.

Reducing risks

In the short term, off-the-shelf flash storage may have the right specs and may cost less than a customised part from a supplier, but there are always hidden costs and risks for the OEM. Flash storage is a critical part for rugged industrial applications and more manufacturers should engage a supplier from the beginning of the design process, to ensure they get what they need for their product’s entire lifecycle.

“Often, industrial OEMs are more focused on designing a high-quality product, and hence do not spend much time considering flash storage,” said Diaz. “But, given the critical nature of data in today’s devices, there’s too much risk to take industrial flash for granted.”

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