From: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
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To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
Cc: | Josh Berkus <josh(at)agliodbs(dot)com>, Magnus Hagander <magnus(at)hagander(dot)net>, Simon Riggs <simon(at)2ndquadrant(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: increasing the default WAL segment size |
Date: | 2016-08-25 18:49:31 |
Message-ID: | 20160825184931.GA270291@alvherre.pgsql |
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Lists: | pgsql-hackers |
Robert Haas wrote:
> On Thu, Aug 25, 2016 at 1:43 PM, Josh Berkus <josh(at)agliodbs(dot)com> wrote:
> > The one thing I'd be worried about with the increase in size is folks
> > using PostgreSQL for very small databases. If your database is only
> > 30MB or so in size, the increase in size of the WAL will be pretty
> > significant (+144MB for the base 3 WAL segments). I'm not sure this is
> > a real problem which users will notice (in today's scales, 144MB ain't
> > much), but if it turns out to be, it would be nice to have a way to
> > switch it back *just for them* without recompiling.
>
> I think you may be forgetting that "the base 3 WAL segments" is no
> longer the default configuration. checkpoint_segments=3 is history;
> we now have max_wal_size=1GB, which is a maximum of 64 WAL segments,
> not 3.
I think the relevant one for that case is the minimum, though:
#min_wal_size = 80MB
which corresponds to 5 segments. I suppose the default value for this
minimum would change to some multiple of 64MB.
--
Álvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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