fsync: Linux vs FreeBSD
Bruce Cran
bruce at cran.org.uk
Tue Oct 26 19:07:11 UTC 2010
On Tue, 26 Oct 2010 15:33:52 -0300 (ADT)
"Marc G. Fournier" <scrappy at hub.org> wrote:
>
> Someone recently posted on one of the PostgreSQL Blogs concerning
> fsync on Linux/Windows/Mac OS X, but failed to make any comments on
> any of the BSDs ... the post has to do with how fsync works on the
> various OSs, and am curious as to whether or not this is something
> that also afflicts us:
>
> http://rhaas.blogspot.com/2010/10/wal-reliability.html
>
> >From reading our man page, I see no warnings similar to what the
> >other OSs
> have, specifically:
>
> Mac OS X: For applications that require tighter guarantees about the
> integrity of their data, Mac OS X provides the F_FULLFSYNC
> fcntl
>
> Linux: If the underlying hard disk has write caching enabled, then the
> data may not really be on permanent storage when fsync() /
> fdatasync() return.
>
> So, do we hide the fact, or are, in fact, not afflicted by this?
Yes, it is a problem:
http://leaf.dragonflybsd.org/mailarchive/kernel/2010-01/msg00007.html
There also a paragraph on write cache and filesystem integrity in da(4):
http://www.freebsd.org/cgi/man.cgi?query=da&apropos=0&sektion=0&manpath=FreeBSD+8.1-RELEASE&format=html
--
Bruce Cran
More information about the freebsd-questions
mailing list