Insufficient space message

Did a system backup, b/u drive is same size as source. When attempting a second b/u following week, get message insufficient space. Do I need to reformat before each b/u? Thought it would overwrite any data there with the current b/u.

 

not sure if there is a setting that overwrites old/previous backup, probably not.

 

To overwrite previous backup each time you need to un-check 'Generate unique names' option in backup settings.

Depending on what kind of backups you use you can simply remove old unnecessary backups to get free space.