Re: patch to allow disable of WAL recycling
| От | Jerry Jelinek |
|---|---|
| Тема | Re: patch to allow disable of WAL recycling |
| Дата | |
| Msg-id | CACPQ5FoKi0L7qwS-i3bGnRBTHF-u3VZ9mr-_OmR3pqqXB-ij+g@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: patch to allow disable of WAL recycling (Alvaro Herrera <alvherre@2ndquadrant.com>) |
| Ответы |
Re: patch to allow disable of WAL recycling
|
| Список | pgsql-hackers |
Alvaro,
I have previously posted ZFS numbers for SmartOS and FreeBSD to this thread, although not with the exact same benchmark runs that Tomas did.
I think the main purpose of running the benchmarks is to demonstrate that there is no significant performance regression with wal recycling disabled on a COW filesystem such as ZFS (which might just be intuitive for a COW filesystem). I've tried to be sure it is clear in the doc change with this patch that this tunable is only applicable to COW filesystems. I do not think the benchmarks will be able to recreate the problematic performance state that was originally described in Dave's email thread here:
Thanks,
Jerry
On Wed, Aug 22, 2018 at 8:41 AM, Alvaro Herrera <alvherre@2ndquadrant.com> wrote:
On 2018-Aug-22, Andres Freund wrote:
> On 2018-08-22 11:06:17 -0300, Alvaro Herrera wrote:
> > 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.
Yeah, but let's see some ZFS numbers first :-)
--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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