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

Magnus Hagander wrote:
> > > 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.

OK, docs updated:

On <productname>Windows</> if <varname>wal_sync_method</> is
<literal>open_datasync</> (the default), write caching is disabled by
unchecking <literal>My Computer\Open\{select disk
drive}\Properties\Hardware\Properties\Policies\Enable write caching on
the disk</>. Also on Windows, <literal>fsync</> and
<literal>fsync_writethrough</> never do write caching.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://postgres.enterprisedb.com

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