Re: Redesigning checkpoint_segments

On Sat, Aug 24, 2013 at 12:08:30AM +0300, Heikki Linnakangas wrote:
> You can also set min_recycle_wal_size = checkpoint_wal_size, which
> gets you the same behavior as without the patch, except that it's
> more intuitive to set it in terms of "MB of WAL space required",
> instead of "# of segments between checkpoints".
>
> Does that make sense? I'd love to hear feedback on how people
> setting up production databases would like to tune these things. The
> reason for the auto-tuning between the min and max is to be able to
> set reasonable defaults e.g for embedded systems that don't have a
> DBA to do tuning. Currently, it's very difficult to come up with a
> reasonable default value for checkpoint_segments which would work
> well for a wide range of systems. The PostgreSQL default of 3 is way
> way too low for most systems. On the other hand, if you set it to,
> say, 20, that's a lot of wasted space for a small database that's
> not updated much. With this patch, you can set "max_wal_size=1GB"
> and if the database ends up actually only needing 100 MB of WAL, it
> will only use that much and not waste 900 MB for useless
> preallocated WAL files.

Where are we on this?

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

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