A data de-duplication application de-duplicates redundant data on the primary storage read/write pathway of a virtualized server environment. The virtualized server environment comprises one or more server applications operating on a virtualization layer provided on a computer architecture that includes memory (e.g., RAM, cache memory) for temporarily storing data and storage (e.g., disk storage) for persistently storing data. The one or more server applications use the read-write pathway to read data into memory from storage and to write data to storage from memory. The de-duplication application identifies redundant data in memory, storage, or both, and replaces the redundant data with one or more pointers pointing to a single copy of the data. The de-duplication application can operate on fixed or variable size blocks of data and can de-duplicate data either post-process or in-line.