SSDs are faster, more convenient, and more power efficient than HDDs for primary use, but they are unreliable for unpowered long term (i.e. cold) storage. If left without power for extended periods, SSDs can suffer from data corruption or loss. For reliable archival storage, users often prefer HDDs, magnetic tape, cloud, or M-Disc.
https://www.xda-developers.com/your-unpowered-ssd-is-slowly-losing-your-data/
