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Re: Changing the default wal_sync_method to open_sync for Win32?

From: "Magnus Hagander" <mha(at)sollentuna(dot)net>
To: "Marc G(dot) Fournier" <scrappy(at)postgresql(dot)org>,"Bruce Momjian" <pgman(at)candle(dot)pha(dot)pa(dot)us>
Cc: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>, <pgsql-hackers(at)postgresql(dot)org>,<pgsql-hackers-win32(at)postgresql(dot)org>,"Merlin Moncure" <merlin(dot)moncure(at)rcsonline(dot)com>
Subject: Re: Changing the default wal_sync_method to open_sync for Win32?
Date: 2005-03-17 08:44:59
Message-ID: 6BCB9D8A16AC4241919521715F4D8BCE6C70B9@algol.sollentuna.se (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-hackers-win32
> >> I'd like to see this one also considered for 8.0.x, though I'd 
> >> certainly like to see some more testing as well. Perhaps it's 
> >> suitable for the "8.0.x with extended testing" that is planned for 
> >> the ARC replacement code?
> >>
> >> It does make a huge difference on win32. While we definitly don't 
> >> want to risk data, a 60% speedup in write intensive apps 
> is a *lot*.
> >
> > Notice we never default to open_sync.  However, on Win32, 
> Magnus got a 
> > 60% speedup by using open_sync, implemented using 
> > FILE_FLAG_WRITE_THROUGH.  Now, because this the fastest on Win32, I 
> > think we should default to open_sync on Win32.  The attached patch 
> > implements this.
> 
> Considering how stable an Operating System Windows *isn't*, I 

The difference has nothing to do with the stability of the OS. It has to
do with wether we ignore the *hardware* write cache or not. Both methods
ignore the OS write cache.


> think the first thing Magnus states very much goes against 
> making this the default: 
> "While we definitely don't want to risk data..." ...
> 
> Setting something like this that increases the risk to data 
> should never be 'the default behaviour', but a conscious 
> decision on the part of the administrator of the individual 
> system ... and even then, with a good skull-n-cross bones 
> warning around it so that they  understand the risks ...

The same level of "risk due to write cache" exists on all other
operating systems already. (Actually, I only know it exists on linux,
but it sure looks like it exists on most others looking at performance
figures)


//Magnus

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