I have neither a Mac, nor the drive in question, but I don't see how what you want to do will help you. What you want to do will not create a backup copy of your data, it will just provide you with a second copy of the data, on the same medium. For the copy to provide any level of data security it has to be stored on a different physical drive. So for a degree of protection you would need to have the file saved on both the internal HDD and the external device.
It sounds to me from the products name as if it basically creates a simple mirroring RAID array, so that everything that is on the "main" drive is also written to the mirror drive at the same time. This provides instant backup for all data should one of the two drives fail, but while operating you should only see it as a single device. Also mirroring is not a backup, since if the file is deleted from the main drive, or is for example encrypted by one of the viruses that work in that way, the mirrored copy will also be deleted or encrypted at the same time.
To be a true backup of your data it should be being checked for integrity and then copied to a separate device. Ideally the backup device is only attached to the computer and powered up during the backup process. You should also be making multiple backups, with one of them kept off site for maximum data security.