Supported file-systems for external hard-drive

Just tried to setup jobs to make an additional backup to an external hard-drive via USB but each time I connect it I get a warning message that the file-system it uses is unsupported and may result in hard-drive failure.  Tried reformating it in NTFS and FAT but still get the warning messages.  Do I need to make a size adjustment or reformat it into some other type of file-system? 

Right after a lot of deleting volumes, reformatting, and changing between GPT and MBR, the EX2 suddenly decided it was now happy with my external hard drive.  Yet, as always with this device, as one problem is solved a new one arises.  Managed to set up a series of backups to copy my most important files to the external hard-drive but now being greeted with a series of ‘backup failed’ messages.  Is there any log file stored somewhere that provides some actual useful information on precisely what the issue is and provide some clue as to what I need to do to get backups to work? 

I have the same problems as long as I use the product . 

Send many complaints,  but the only anwer is,  that you have to sent logs and pics. 

After that,  nothing.

I also got a error message that the fan is not working,  and they promised me a response email back. 

Never received one. 

Now if I make a backup,  i have to click 6 times to make it start. 

You must wait for a minute to let it finally start. (for that time it looks like nothing happens!) 

And at the end,  when you got a failure,  you are getting no information whatsoever. 

You will have to start over again,  until it ends without a failure. 

And the next time you want a new bu,  it starts all over again. 

WD isn’t really interested! 

I’m saving money for a better product.