Re: Simplifying wal_sync_method

Joshua D. Drake wrote:
> 
> >>>I think we should offer the reliable option by default, and mention the
> >>>fast option for those who have battery-backed cache in the manual.
> >>
> >>But only on Win32?
> > 
> > 
> > Yes, because that's the only place where that option works, right?
> 
> fsync_writethrough only works on Win32 the postgresql.conf should 
> reflect that.

Right now what wal_sync_method supports isn't clear at all.  If you have
fdatasync or O_DSYNC (and it has a different value from O_SYNC/O_FSYNC),
you have those, if not, you get an error.  For example, my system
doesn't have fdatasync(), so if I try to use that value I get this in my
server logs:

	FATAL:  invalid value for parameter "wal_sync_method": "fdatasync"

and the server does not start.  Also, writethrough is supported in 8.1
by both Win32 and OS X.

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