There is not enough disk space to create the volume shadow copy on the storage location. Make sure that, for all volumes ...

There is not enough disk space to create the volume shadow copy on the storage location. Make sure that, for all volumes to be backup up, the minimum required disk space for shadow copy creation is available. This applies to both the backup storage destination and volumes included in the backup.
Minimum requirement: For volumes less than 500 megabytes, the minimum is 50 megabytes of free space. For volumes more than 500 megabytes, the minimum is 320 megabytes of free space. 
Recommended: At least 1 gigabyte of free disk space on each volume if volume size is more than 1 gigabyte.