DATA RECOVERY SSD disk

SSDs or solid-state drives have a limited lifespan, linked to the number of write cycles performed by the medium. The electrical resistance of storage cells increases with each reuse, as data is deleted and rewritten. The voltage required for each new write operation thus increases over time. Storage cells reach their electrical limits and eventually become unusable.

There are several levels of storage cells, with varying lifetimes, their capacity being at the expense of the number of write cycles they can support:

• the SLC(Single Level Cell ), with a capacity of 1 bit, supports up to 100,000 write cycles; it is reputed to be the fastest, longest-lasting and most resilient;
• the MLC(Multi level cell ) has a capacity of 2 bits and can undergo up to 10,000 write cycles;
• the TLC(Triple Level Cell ), with a capacity of 4 bits, can only support 3,000 write cycles;
• the QLC(Quad Level Cell ), with a capacity of 3 bits, guarantees a maximum of 1,000 write cycles.

To overcome this shortcoming, SSD disks feature an internal controller, which manages memory accesses. It is used for data transfers (write, read, erase), but also to check that the device is working properly. This controller uses several techniques to limit wear and tear on flash memory, such as :

• Wear Levelling, which consists of randomly distributing data on free storage cells, and recording their frequency of use and wear, in order to find the free blocks that have undergone the fewest cycles during write operations;
• Bad Block Management, which identifies at-risk storage cells, marks them as faulty and replaces them with cells from a reserve contained on the SSD;