Loaded footgun open_datasync on Windows

From: Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at>
To: pgsql-hackers(at)postgresql(dot)org
Subject: Loaded footgun open_datasync on Windows
Date: 2018-06-01 09:43:33
Message-ID: 1527846213.2475.31.camel@cybertec.at
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I recently read our documentation about reliability on Windows:

> On Windows, if wal_sync_method is open_datasync (the default), write caching can
> be disabled by unchecking
> My Computer\Open\disk drive\Properties\Hardware\Properties\Policies\Enable write caching
> on the disk. Alternatively, set wal_sync_method to fsync or fsync_writethrough,
> which prevent write caching.

It seems dangerous to me to initialize "wal_sync_method" to a method that is unsafe
by default. Admittedly I am not a Windows man, but the fact that this has eluded me
up to now leads me to believe that other people running PostgreSQL on Windows might
also have missed that important piece of advice and are consequently running with
an unsafe setup.

Wouldn't it be smarter to set a different default value on Windows, like we do on
Linux (for other reasons)?

I am worried that there might be loads of Windows installations out there happily
running productive databases with an unsafe setup, so I'd even suggest backpatching
such a change.

Laurenz Albe


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