Blackmagic Disk Speed Test
is a tool for checking the performance of a hard drive. Designed for Macintosh, this tool uses a standard method to determine the reading and writing speed of your hard drive.
In order to do this, it only fills in the free space on your hard disk by a sample of data and begins the assessment to determine these two parameters. Note that this test is particularly useful to certify the performance of your hard disk for working with high quality video.
Blackmagic Disk Speed Test is also available to download on Mac here