NAND wears out. MLC wears out faster than SLC. The vendors obfuscate which type they use. New wear leveling algorithms help, but cannot eliminate this issue.
NAND can only block erase, this is the reason for write performance issues.
Do not go into Flash based storage without this understanding.
P.S. Cobalt doped gamma hematite drives have been gone for over a decade so "Spinning Rust" no longer applies.
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