Actually on many OSes it's a 'start a background force to disk now and return before it's done' operation; on Linux it's a 'lob it at the disk controller so it can cache it instead' operation. Still not necessarily useful (although that is changing to optionally emit a barrier to the disk controller too.)
(Speaking as the owner of an Areca RAID card with a quarter-gig of battery-backed cache, using non-RAIDed filesystems purely as an fs-cache storage area, I *like* the ability to turn off barriers: all they do is slow my system down with no reliability gain at all.)
Copyright © 2018, Eklektix, Inc.
Comments and public postings are copyrighted by their creators.
Linux is a registered trademark of Linus Torvalds