Heikki,
On Monday, March 2, 2015, Heikki Linnakangas <
hlinnaka@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 (robertmhaas@gmail.com) wrote:
On Mon, Mar 2, 2015 at 6:43 AM, Heikki Linnakangas <hlinnaka@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