Re:The Shingled magnetic recording NAS debacle
by bcrl on Thursday May 28, 2020 @06:23PM
(#23343582)
That is a bit of a naive understanding of flash failure modes that is, unfortunately, incorrect. SSDs can lose data purely through read-only workloads. Flash suffers from read disturbances (just like the DRAM row hammer attack). Cells are not perfect, and electrical charge from adjacent rows/cells can leak. As a result, even idle data needs to be refreshed in SSDs. This is a case where there are major differences in the behaviour of NAND vs NOR flash, with NAND flash being more vulnerable.
There are also documented cases of Intel SSDs that should have gone read-only once reaching the end of their wear life failing outright due to firmware bugs. As is usually the case, software failures in corner cases abound.
Flash doesn't fail when it wears out. SSDs simply become read only and get slower over time when they exhaust their write cycles. That's not a failure. A failure is something like your SSD controller bricking itself randomly during a power cut and instantly making all your data vanish.