Problem with Comparison of two Drives

[mitrajoon]

I'm a new user. I first backed up my internal Data drive to two different external back up drives. I then ran a comparison run between the two drives to double check that they were identical. However many of my files in one external backup drive had a notation "can not find file".

I then started checking for the files that could not be found. I checked about a half dozen files, none was missing, all were where they were supposed to be. I then checked the same files in other backup drive and they were there as well.

I am running W10 on a Dell Computer.

Can anybody explain this? What should I do to make sure my files are intact on two different backup drives?