Re: data_checksums enabled by default (was: Move --data-checksums to common options in initdb --help)

On Wed, Jan 6, 2021 at 8:31 AM Michael Banck <michael(dot)banck(at)credativ(dot)de> wrote:
>
> Hi,
>
> Am Mittwoch, den 06.01.2021, 10:52 +0900 schrieb Michael Paquier:
> > On Mon, Jan 04, 2021 at 07:11:43PM +0100, Michael Banck wrote:
> > > So maybe we should switch on wal_compression if we enable data checksums
> > > by default.
> >
> > I don't agree with this assumption. In some CPU-bounded workloads, I
> > have seen that wal_compression = on leads to performance degradation
> > with or without checksums enabled.
>
> I meant just flipping the default, admins could still turn off
> wal_compression if they think it'd help their performance. But it might
> be tricky to implement, not sure.

The other argument is that admins can cheaply and quickly turn off
checksums if they don't want them.

The same cannot be said for turning them *on* again, that's a very
slow offline operation at this time.

Turning off checksums doesn't take noticeably more time than say
changing the shared_buffers from the default, which is also almost
guaranteed to be wrong for most installations.

--
Magnus Hagander
Me: https://www.hagander.net/
Work: https://www.redpill-linpro.com/