This is a basic gist for testing the disk speed of your system. It writes a pre-specified quantity of MB to the drive and measures the time. Following that, it then reads the same bytes to see how long it takes as well. I got this off of a random forum a long, long time ago and have modified it a bit as the time has passed; it's pretty handy.

disk_speed.sh

#!/bin/bash

# Jordan Westhoff, RIT 2014

read -p "Batch size for test (enter in MB) {1024MB in a GB}" sze

echo "Testing Disk Speed"
echo "$sze MB sample size"

  dd if=/dev/zero of=test bs=1048576 count=$sze
  dd if=test of=/dev/null bs=1048576

echo "Disk Speed Check Complete"