Techniques and mechanisms are provided to instantly clone active files including active optimized files. When a new instance of an active file is created, a new stub is generated in the user namespace and a block map file is cloned. The block map file includes the same offsets and location pointers that existed in the original block map file. No user file data needs to be copied. If the cloned file is later modified, the behavior can be same as what happens when a de-duplicated file is modified.