Re: Benchmarking

> I need to check the scalability of a machine with postgresql and Im doing it
> with pgbench but Im getting values with a variation of a 40% with the same
> pgbench call...

You might be looking at the effect of the kernel buffer cache. Try run
pgbench several times with same settings. Another point is how many
transactions pgbench runs (-t option). More transactions would give
more statble results. Here is my small script to run pgbench. I
usually run it 2 or 3 times and take only the last run result.

#! /bin/sh
pgbench -i -s 2 test
for i in 1 2 4 8 16 32 64 128
do
t=`expr 640 / $i`
pgbench -t $t -c $i test
echo "===== sync ======"
sync;sync;sync;sleep 10
echo "===== sync done ======"
done