When you’re ready to do more advanced tests than simple time tests, go get bonnie++ at http://www.coker.com.au/bonnie++/. Read the documentation! And understand that the most important thing it’s measuring is CPU usage. High usage means the choking point is the CPU itself. Low numbers mean the problem is, well, somewhere else. But the gist of it is that you want to find options that lower your CPU usage.
bonnie++ is a very good starting point, but the most comprehensive test you can find in this area is iozone. Get it at http://www.iozone.org/. This utility produces spreadsheet-compatible files that you can examine or graph in OpenOffice’s Calc or Microsoft’s Excel.