> the war stories that PostgreSQL developers could tell about disk syncing. The man page for glibc open(2) used to say, "Most Linux filesystems don't actually

> the war stories that PostgreSQL developers could tell about disk syncing. The man page for glibc open(2) used to say, "Most Linux filesystems don't actually implement the POSIX O_SYNC semantics, which require all metadata updates of a write to be on disk on returning to userspace", but now it notes that "before Linux 2.6.33" it wasn't implemented correctly I remember a rather eye-opening discussion on either the postgresql-hackers or lkml about the semantics of O_SYNC not actually being synchronous. In addition to the implementation details, which depended on the version of the kernel and the underlying filesystem type, it was also noted that underlying disk hardware also had caches which did not necessarily behave synchronously. Some places I can find that cover these details include https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg272253.html https://www.mail-archive.com/linux-kernel@vger.kernel.org/ms... http://milek.blogspot.com/2010/12/linux-osync-and-write-barriers.html http://milek.blogspot.com/2010/12/linux-osync-and-write-barr... https://lwn.net/Articles/352229/ https://lwn.net/Articles/352229/