NetApp ONTAP includes an advanced suite of storage efficiency technologies embedded directly within the Write Anywhere File Layout (WAFL) filesystem architecture. NetApp deduplication is the specific storage efficiency feature engineered to search for and eliminate duplicate 4KB data blocks across a FlexVol or FlexGroup volume, or across an entire local tier (aggregate).

ONTAP deduplication operates by generating cryptographic digital fingerprints (hashes) for all written 4KB blocks and storing them in an internal fingerprint database. When duplicate fingerprints are detected—either in real time (inline deduplication) before writing to media or during post-process background scans (background deduplication)—ONTAP verifies the block contents. It then retains a single physical block on disk, updates WAFL metadata pointers so that all duplicate logical blocks point to that shared physical block, and releases the redundant physical space back to the storage pool. Compression reduces the physical footprint of individual blocks by encoding repetitive patterns using LZ-based algorithms. Compaction aggregates multiple sub-4KB data chunks into a single 4KB physical block, and thin provisioning allocates storage on demand rather than eliminating duplicate data.