Acronis Nonstop Backup and defragmentation are fully compatible and do not interfere
It is not recommended to use disk defragmentation if you back up to the Acronis online storage and the disks are of considerable size.
If you run disk defragmentation after creating a disk/partition backup, the succeeding incremental backup will roughly be the size of the full backup. For detailed information please see Acronis Backup Software Creates Large Incremental or Differential Backup Archives.
Incremental or differential backups are larger when performed after disk defragmentation or full restore