When you are creating the backup file of your Mac computer in an external usb drive but it failed to backup usb drive on Mac and you don't know what to do in this situation then you have come to tight place. Well, it is really very good effort to maintain the backup file because now a data loss has became a very famous issue. There are some issues that causes failed to backup usb drive on Mac. Some of the time it happens due to incorrect connection of usb drive with the computer. If the usb drive is not compatible with your Mac system then also this could happen. There is also a possibilities of failed to backup usb drive on Mac when the usb drive is infected with virus. You should change the another usb drive for creating the backup file from Mac. System file corruption and incomplete upgrade of Mac os might be te cause of failed to backup usb drive on Mac. Let me tell you one thing that if any problem in your Mac system leads to data loss situations then you are requested to use a third party software which is popular with the name of Mac data recovery software. In every versions of Mac computers is easily suitable.