If you just want to see my top picks, skip to the Overall Picks section. If you want to read in more detail about how I determined the top picks, rea

On the Capacity, Performance, and Reliability of microSD Cards

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2024-11-21 13:30:14

If you just want to see my top picks, skip to the Overall Picks section. If you want to read in more detail about how I determined the top picks, read on.

MicroSD cards are ubiquitous nowadays, having found applications in a wide variety of consumer devices — including smartphones, digital cameras, and single-board computers. While innovation is continuing to take place in this space, the market has largely matured. There are a wide variety of brands, models, and capacities available today, but it could be argued that consumers see little difference — aside from capacity — from one brand or model of card to the next. This ubiquity has helped to drive prices down to the point where a card able to store hundreds of gigabytes of data can be obtained for less than the price of a single meal at an average restaurant.

As with any popular product, the market is littered with fakes. For example, 1 terabyte microSD cards from major brands — such as SanDisk or Lexar — cost around $70-$100, depending on the specific brand or model. A cursory search on Amazon for a 1 TB microSD card, however, yields off-brand (or no-brand) cards with prices as low as $12.99. How are these brands able to offer their products for far less than their name-brand competitors? In many cases, these cards are what is known as “fake flash” — cards that have been programmed to advertise a certain capacity to their host device, but whose actual capacity is far less. For example, a card advertised as having a capacity of 1 terabyte might have an actual capacity closer to 8 gigabytes. On these cards, the actual storage space is typically located at the beginning of the card’s logical address space; writes that occur beyond the end of the available space are simply discarded, while reads will typically result in all zeroes. Additionally, most filesystem implementations will fill up the available space in a linear fashion. Altogether, this means that the user might not notice anything wrong until they’ve filled the card’s physical space — at which point they will find that the data that was saved beyond the end of the card’s physical space is simply gone and unrecoverable.