I'm trying to compare different filesystems for postgres using pgbench. The problem I've seen is that my IO wait is very very low. Is there a way I can get pgbench to do more to push that up a little?
Why do you expect to see high IO wait?
Does your database fit in system memory? If you do not modify the data and it is not large enough, it is unlikely you will hit IO wait.
Do you have write cache enabled for the file system/device? Even if you have some DML statements, it would not be that easy to saturate write cache enabled storage (especially, when it fits in memory).
Regards,
Vladimir Sitnikov