Fil Trailer

The Fil Trailer has one part, as follows:






low 4 bytes = checksum of page, last 4 bytes = same as FIL_PAGE_LSN

The final part of a page, the fil trailer (or File Page Trailer), exists because InnoDB's architect worried about integrity. It's impossible for a page to be only half-written, or corrupted by crashes, because the log-recovery mechanism restores to a consistent state. But if something goes really wrong, then it's nice to have a checksum, and to have a value at the very end of the page which must be the same as a value at the very beginning of the page.