About SSD power loss

Risks of unexpected power loss on solid state drives

Each time data is accessed or modified on the SSD, metadata is modified pertaining to the state of the data. This information allows for the storage controller to choose what data should be in the drive’s volatile cache at any given moment as well as the ability to implement techniques which increase performance and endurance

The drive then translates the LBA to the Physical Block Address (PBA) by way a flash translation table (FTL). The FTL is stored in cache and it is the responsibility of the controller to flush this table to non-volatile memory at times it deems appropriate or during a clean shutdown. The metadata associated with each page of data written also has information that can be used to rebuild the FTL if it is lost, but this rebuild takes time at the next power-on. If both the FTL and metadata are corrupted due to a sudden power loss event, the data stored on the SSD can become lost or even worse, the SSD, as a whole, can become inaccessible

Turning drive cache off
Pros: Data integrity is preserved in the event of a sudden power loss.
Cons: Dramatic decrease in read and write performance.
Increased writes to NAND resulting in lower write endurance and decreased drive life. FTL data is still stored in the volatile cache, which leaves it at risk

Capacitor hold-up circuitry
Pros: Data integrity is preserved in the event of a sudden power loss.
Cons: Increased cost due to inclusion of additional circuitry including capacitors. Additional board space is required.

Dell Solid-State-Drive-FAQ