Re: Document how to turn off disk write cache on popular operating

On Tue, Dec 11, 2007 at 08:18:42AM -0500, Bruce Momjian wrote:
> Magnus Hagander wrote:
> > On Mon, Dec 10, 2007 at 02:05:05PM +0000, Bruce Momjian wrote:
> > > Log Message:
> > > -----------
> > > Document how to turn off disk write cache on popular operating systems.
> > > 
> > > Modified Files:
> > > --------------
> > >     pgsql/doc/src/sgml:
> > >         wal.sgml (r1.46 -> r1.47)
> > >         (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/wal.sgml?r1=1.46&r2=1.47)
> > 
> > Should this mention that you don't need to turn it off at the disk level if
> > you use fsync_writethrough? 
> 
> Uh, I remember we looked at this checkbox before but I don't remember
> the details, and I can't find a comment about it.  Was the issue that
> writethrough always forces through the disk cache?  Is that the default
> on Win32?  Did we comment this somewhere?

If you set it to fsync or fsync_writethrough it will write through the
cache. (fsync is just an alias)
If you set it to OPEN_DATASYNC, it will respond to the checkbox you are
referring to.

OPEN_DATASYNC is the default, IIRC.

//Magnus