NOTE
MySQL Files and Durable Storage
How database files, redo/binlog, tablespaces, filesystem caches, and fsync interact.
This is a historical learning note and may contain outdated or incomplete understanding.
MySQL durability ultimately depends on files written through the operating system and storage stack: data/tablespace files, redo, binary logs, undo/temp structures, and metadata. The exact files/layout depend on engine and version.
A successful write() does not necessarily mean data is on nonvolatile media; durability settings determine when MySQL requests synchronization and what acknowledgements mean. Filesystem/storage behavior therefore matters to crash guarantees and latency.