Here is a small Linux command that I have used frequently to look at disk performance on some of my Linux servers.
iostat -xdkt 30 360 >> iostat-results.txt
The above command will start a program called iostat and gather extended attributes for all disks on a machine every 30 seconds for 360 iterations and then write (append) the results to the iostat-results.txt file. That file can then be manipulated in your favorite text program and even imported to a spreadsheet for review.
I run this on Redhat and Centos servers but iostat can be installed on may other linux distributions.
Hope this helps.