Heikki, On Monday, March 2, 2015, Heikki Linnakangas <hlinn...@iki.fi> wrote:
> On 03/02/2015 08:05 PM, Josh Berkus wrote: > >> On 03/02/2015 05:38 AM, Stephen Frost wrote: >> >>> * Robert Haas (robertmh...@gmail.com) wrote: >>> >>>> On Mon, Mar 2, 2015 at 6:43 AM, Heikki Linnakangas <hlinn...@iki.fi> >>>> wrote: >>>> >>>>> On 02/26/2015 01:32 AM, Josh Berkus wrote: >>>>> >>>>>> But ... I thought we were going to raise the default for max_wal_size >>>>>> to >>>>>> something much higher, like 1GB? That's what was discussed on this >>>>>> thread. >>>>>> >>>>> >>>>> No conclusion was reached on that. Me and some others were against >>>>> raising >>>>> the default, while others were for it. >>>>> >>>> >>>> I guess that's a fair summary of the discussion, but I still think >>>> it's the wrong conclusion. Right now, you can't get reasonable write >>>> performance with PostgreSQL even on tiny databases (a few GB) without >>>> increasing that setting by an order of magnitude. It seems an awful >>>> shame to go to all the work to mitigate the downsides of setting a >>>> large checkpoint_segments and then still ship a tiny default setting. >>>> I've got to believe that the number of people who think 128MB of WAL >>>> is tolerable but 512MB or 1GB is excessive is almost nobody. Disk >>>> sizes these days are measured in TB. >>>> >>> >>> +1. I thought the conclusion had actually been in favor of the change, >>> though there had been voices for and against. >>> >> >> That was the impression I had too, which was why I was surprised. The >> last post on the topic was one by Robert Haas, agreeing with me on a >> value of 1GB, and there were zero objections after that. >> > > I didn't make any further posts to that thread because I had already > objected earlier and didn't have anything to add. > > Now, if someone's going to go and raise the default, I'm not going to make > a fuss about it, but the fact remains that *all* the defaults in > postgresql.conf.sample are geared towards small systems, and not hogging > all resources. The default max_wal_size of 128 MB is well in line with e.g. > shared_buffers=128MB. > Not to be too much of a pain, but I've run into very few systems where memory and disk are less than an order of magnitude different in size. I definitely feel we need to support users tuning their systems for smaller sizes but I do think our defaults are too small for the majority. Thanks! Stephen