Good SD cards can go bad for a variety of reasons. There is a long list of potential culprits in situations like this, ranging from “you ejected the card too suddenly” to “the card just got old and died”. It could be a simple logical issue of a sector with filesystem metadata going corrupt to a physical issue in which key filesystem sectors have died out. While the NAND flash memory chips inside SD cards are far more resilient than hard disk drives with their sensitive moving parts, even flash devices can break down. Ultimately, when an SD card becomes corrupt, there’s no telling what type of damage it’s suffered, or how severe the damage is “under the hood”. In these situations, it’s best to leave the task of SD card file recovery to data recovery specialists.
SD cards don’t have little hard disk drives inside them. There’s only so much you can do to shrink a hard drive’s components—and why go through all the hard work of designing a tiny hard drive when you can just use an even tinier flash memory chip? But just like anything else, flash chips can wear out and break down, putting the user’s data in jeopardy.
The smallest unit of data storage in a flash memory chip is a single cell, which consists of a single NAND or NOR transistor. Traditionally, a single cell held a single bit of data. In multi-level cells, though, a one cell can contain two or three bits of data. This doubles or triples the capacity of the chip without increasing its size or the amount of cells it contains. This is great for manufacturers (and consumers) because it makes higher-capacity flash devices cheaper to both produce and purchase. But it comes at a price—MLC chips tend to wear out faster than SLC (single-level cell) chips.
If enough flash memory cells become unreadable, the entire chip can become corrupt. This can happen not as a result of any misuse or mishandling by the user, but just due to rotten luck and the inexorable march of time. All data storage devices break down sooner or later. As long as entropy remains a law of the cosmos, that fact will not change. Sometimes you’re just unfortunate enough that it happens to you sooner rather than later.
The client in this data recovery case study was a professional photographer. They had just returned from a photoshoot, eager to copy their work over to their computer. About 500 photos lived on the SD card they’d kept inside their camera. But when they inserted the SD card from their camera into their computer’s SD card slot, they encountered an error. According to the client’s PC, their SanDisk Extreme Pro SD card was corrupt and unreadable. The client contacted the corrupted SD card recovery specialists at our data recovery company to see what we could do to remedy their situation.
Our engineers found physical damage to the cells of the client’s corrupted SD card. This damage hadn’t been caused by any sort of physical trauma, but just unfortunate wear on the chips. This physical damage had rendered a handful of sectors governing critical filesystem data unreadable, including the file definitions and directory structure. Basically, due to the physical damage, the links in the logical chain pointing to the locations of the client’s files had been obliterated.
But the client’s data still lived somewhere on the chip, and our SD card file recovery engineers knew how to find it. Our SD card recovery specialists can configure our data recovery software tools to scan the disk image we created of the corrupt SD card and search for JPEG file headers. Every file’s first sector contains a short “header” identifying what type of file it is and how it should be treated. Using this recovery method, our data recovery experts can find every instance where the header occurs in the entire drive and pull any associated files out of the raw binary data.
Our engineers uncovered around 500 JPEG image files from the 99.9%-complete disk image we’d made of the client’s SD card. We sent the client thumbnails of our recovery results so they could see for themselves the quality of our recovery efforts. Our technicians had found and successfully recovered all of the client’s photos from their corrupt SD card. We rated this corrupted SD card recovery case a perfect 10 on our ten-point scale.