To perform live backup you need to:
1. Take a snapshot of running VM. Right click on VM -> Snapshot -> Create snapshot.
2. Login to the host with SSH
3. mkfstools -i source.vmdk -d thin /vmfs/volumes/backup/sameVM.vmdk
4. Wait till cloning is done
5. Don't forget to copy soruce.vmx and source.vmxf files to backup directory
6. Remove snapshot from running VM. Right click on VM -> Snapshot Manager -> Remove ALL
You done!