Re: Remove fsync ON/OFF as a visible option?

On 22/03/15 05:42, David G. Johnston wrote:
> On Sat, Mar 21, 2015 at 8:54 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us
> <mailto:tgl(at)sss(dot)pgh(dot)pa(dot)us>>wrote:
>
> Stephen Frost <sfrost(at)snowman(dot)net <mailto:sfrost(at)snowman(dot)net>> writes:
> > At the moment, one could look at our default postgresql.conf and the
> > "turns forced synchronization on or off" and think it's
> something akin
> > or somehow related to synchronous_commit (which is completely
> different,
> > but the options are right next to each other..).
>
> > How about a big warning around fsync and make it more indepenent
> from
> > the options around it?
>
> Yeah, the main SGML docs are reasonably clear about the risks of
> fsync,
> but postgresql.conf doesn't give you any hint that it's
> dangerous. Now
> I'm not entirely sure that people who frob postgresql.conf without
> having
> read the docs can be saved from themselves, but we could do something
> like this:
>
> # - Settings -
>
> #wal_level = minimal # minimal, archive,
> hot_standby, or logical
> # (change requires restart)
> #fsync = on # turns forced
> synchronization on or off
> + # (fsync=off is dangerous,
> read the
> + # (manual before using it)
> #synchronous_commit = on # synchronization level;
> # off, local,
> remote_write, or on
> #wal_sync_method = fsync # the default is the first
> option
> # supported by the
> operating system:
>
> Also, I think the short description "turns forced synchronization
> on or
> off" could stand improvement; it really conveys zero information.
> Maybe
> something like "force data to disk when committing"?
>
> Also, whatever we do here should be reflected into the description
> strings
> in guc.c.
>
>
> " ​enables or disables data durability ​promise of ACID." ?
>
> David J.
>
>
What does ACID mean???

I don't want to trip out on acid, and if I do, I don't want it hanging
around. Safer to set this to off!!!

I actual do know what ACID means, but some 'children' have write access
to a the postgresql.conf file without adequate 'adult' supervision!

Cheers,
Gavin