On 10/28/2012 10:50 PM, Peter Geoghegan wrote:
On 28 October 2012 22:35, Jan Wieck <janwi...@yahoo.com> wrote:
The amount of WAL generated with full_page_writes=on is quite substantial.
For pgbench for example the ratio 20:1. Meaning with full_page_writes you
write 20x the amount you do without.
Sure, but as always, pgbench pessimises everything by having writes
follow a uniform distribution, which is completely unrepresentative of
the natural world. This will literally maximise the number of pristine
full page images that need to be included. The actual frequency of
checkpoints is a crucial factor here too, and you didn't mention
anything about that.
Higher buffer cache hit rates certainly reduce that ratio.
Well, I guess it was just one of those random thoughts that can't work
in the end or aren't worth the work anyway.
Jan
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