If you have paid attention so far, you may have noticed that the capacity improvements with each technological leap tapers off. However, each increase in the number of cell charge states comes with drawbacks. You can think of a flash memory cell as a book.
With TLC, meanwhile, the book stays about the same thickness, but features eight thin pages — each with three times as many characters as those in the SLC book. Since the pages are so much thinner, they tear easily, and since there is so much more information to flip through, it takes longer to find and read the earmarked page. With each increase in the number of cell charge states, read and write times increase. Decreasingly small voltage differences between each cell charge state also means that it takes minor wear and tear before data integrity is at risk.
In SLC, meanwhile, there are only two cell charge states, making electron leakage to alter the cell charge state much less likely than in the more densely packed MLC, TLC, and so on.
Looking at the graph above, SLC looks like the clear winner for everything except capacity, whereas if capacity is the primary consideration, TLC and everything that comes after it should be the best choice.
In practice, however, things are more nuanced than that. Depending on where and how the flash storage device will be used, any one of the flash types may prove to be the most suitable one.
In video hosting, for example for streaming, however, TLC may prove an excellent alternative as files are written to the drive at rare occasions before being read time after time as users stream the video files. While the differences between flash types are clear, the reality in the flash storage market is that there are a lot more factors that come into play when you figure out what the ideal storage device for your application is.
For example, firmware and hardware enhancements can change the attributes and performance of flash devices very considerably, ensuring that they are optimized for their operating environments. This unique architecture allows cheaper MLC flash to gain some of the benefits of SLC flash, for example better performance and higher endurance. While, technically, still a type of MLC flash, iSLC clearly illustrates why it is unfair to treat all flash storage devices with the same flash types as fully comparable.
A solid-state-storage program-erase cycle is a sequence of events in which data is written to solid-state NAND flash memory cell such as the type found in a so-called flash or thumb drive , then erased, and then rewritten. Program-erase PE cycles can serve as a criterion for quantifying the endurance of a flash storage device.
Flash memory devices are capable of a limited number of PE cycles because each cycle causes a small amount of physical damage to the medium. This damage accumulates over time, eventually rendering the device unusable. The number of PE cycles that a given device can sustain before problems become prohibitive varies with the type of technology. Assured Systems is a leading technology company offering high quality and innovative applied computing solutions to the embedded, industrial, and digital-out-of-home markets around the world via offices in Europe and the Americas.
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