You may receive the following error while backing up any server using Idera (previously know as R1soft):
An exception occurred during the request. An error occurred during the asynchronous execution of VSS operation 'VssWrapper::DoSnapshotSet'. VSS_E_INSUFFICIENT_STORAGE - There are not enough contiguous blocks on disk to create a shadow copy. This problem can usually be resolved by freeing up space and defragmenting the associated volume.
The root causes of this error are as follow:
 If your server (which is being backed up) has in sufficient storage in the volume, it fails to create snapshot and you receive the above error. In such event, you will have to remove the unwanted data or you will have to add addition storage to your server.
 Your drive is highly fragmented. In such case, you can run disk defragmentation.