pub fn write_snapshot_bak(dir: &Path, bytes: &[u8]) -> Result<()>Expand description
Write bytes to snapshot.bin.bak atomically with full fsync.
Uses RealFs::write_atomic which applies F_FULLFSYNC on macOS and
sync_all on other platforms, then renames the .tmp file into place and
syncs the directory entry. This is the only correct path for writing the
.bak — plain std::fs::write + sync_all misses both F_FULLFSYNC and
the directory sync.