Re: patch to allow disable of WAL recycling

On 2018-08-22 11:06:17 -0300, Alvaro Herrera wrote:
> On 2018-Aug-21, Jerry Jelinek wrote:
>
> > Tomas,
> >
> > Thanks for doing all of this testing. Your testing and results are much
> > more detailed than anything I did. Please let me know if there is any
> > follow-up that I should attempt.
>
> Either I completely misread these charts, or there is practically no
> point to disabling WAL recycling (except on btrfs, but then nobody in
> their right minds would use it for Postgres given these numbers anyway).
> I suppose that the use case that was initially proposed (ZFS) has not
> yet been tested so we shouldn't reject this patch immediately, but
> perhaps what Joyent people should be doing now is running Tomas' test
> script on ZFS and see what the results look like.

IDK, I would see it less negatively. Yes, we should put a BIG FAT
warning to never use this on non COW filesystems. And IMO ZFS (and also
btrfs) sucks badly here, even though they really shouldn't. But given
the positive impact for zfs & btrfs, and the low code complexity, I
think it's not insane to provide this tunable.

Greetings,

Andres Freund