Can Flash Drives Be Corrupted?
Flash drives, also known as USB storage devices, are used everywhere from schools to businesses to store everything from music to complete operating systems. With so much relying on the information stored on flash drives, data corruption is a sobering concern. There are some issues inherent to flash drives. Although these do not affect most people or the way they use their flash drives, you should be aware of the capabilities of these tools.
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How Flash Drives Work
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When saving to a flash drive, information passes from your computer‘s USB port into the device. Inside of the flash drive, a memory controller accepts the data and acts as an interface between the “virtual” address of the host system and the physical memory address within Nand flash memory chips contained in the flash drive. The memory controller manages interactions between the flash drive and the host system by reading and sending or writing and saving data as required.
Issues with Nand Technology
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Although Nand-based memory chips are fast and reliable, they do experience memory wear, which is the degradation of the individual Nand flash memory cells within the memory chips. Each time data writes to an individual memory cell, it takes a little more wear. Eventually, with enough wear, the memory cells in the Nand flash chip will fail. Once this occurs there is no repair; the data in that cell is gone forever.
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SLC Nand Flash
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Single layer cell memory (SLC) allows for as many as 100,000 writes to an individual memory cell before corruption occurs. SLC memory chips are of a monolithic nature (single die) with each memory cell storing only a single bit of data in the form of a “1” or a “0“. SLC Nand flash chips are the most expensive to produce, especially in larger capacities, and are physically larger than equal capacity MLC Nand flash chips.
MLC Nand Flash
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Multi-level cell memory (MLC) is physically the smallest Nand flash and allows approximately 10,000 writes to its memory cells before failure. MLC chips are a “stacked” technology with multiple dies of memory cells staked atop one another in the chip. Hence, MLC Nand flash can store two or more bits of data per cell. By staking dies of memory cells, MLC chips can store a much larger amount of data in the same physical space than can a SLC based chip with a reasonable sacrifice in read/write speed.
Wear Leveling
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Designers are always looking to improve flash drives and wear leveling is one of their developments. Wear leveling ensures that all memory cells are used an equal number of times so no one cell fails long before others. The effectiveness of wear leveling depends on how full you keep your flash drive. It you rewrite it to its fullest capacity every cells gets used. If your drive is half-filled, the memory controller can write twice using each cell only once.
Personal Use
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According to Kingston Technology Corp., completely rewriting your flash drive every day would take 10,000 days or over 27 years to wear out the device. Whether you intend to use your flash drive to that extent, there is a simple rule that has proven to be dead-on regardless of the state of memory technology. Back up your data.
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- Photo Credit usb drive#2, isolated image by Oleg Verbitsky from Fotolia.com
