On 2013-05-15 16:46:33 -0500, Jon Nelson wrote:
> > * Is wal file creation performance actually relevant? Is the performance
> >   of a system running on fallocate()d wal files any different?
> In my limited testing, I noticed a drop of approx. 100ms per WAL file.
> I do not have a good idea for how to really stress the WAL-file
> creation area without calling pg_start_backup and pg_stop_backup over
> and over (with archiving enabled).

My point is that wal file creation usually isn't all that performance
sensitive. Once the cluster has enough WAL files it will usually recycle
them and thus never allocate new ones. So for this to be really
beneficial it would be interesting to show different performance during
normal running. You could also check out of how many extents a wal file
is made out of with fallocate in comparison to the old style method
(filefrag will give you that for most filesystems).


Andres Freund

 Andres Freund                     http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services

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