gistfile1.txt

1) alter postgresql.conf
    checkpoint_segments = 100
    checkpoint_completion_target = 0.9
    appropriate shared_buffers

2) initialize pgbench with pgbench -s 1000 -i bench
   
   do one run on the SSD, and if that looks good, one on the HDD

3) run pgbench test with:

pgbench -j 6 -c 24 -l --aggregate-interval=10 -T 1200 bench

4) run iostat and/or sar -d will the above is running, and check for apparent "stalls".

5) check the pgbench logs after the test run and look for huge (> 20%) differences in throughput between summary lines.