Deduplication is a Data ONTAP feature that reduces the amount of physical storage space required by eliminating duplicate data blocks within a FlexVol volume.
Deduplication works at the block level on an active file system, and uses the WAFL block-sharing mechanism. Each block of data has a digital signature that is compared with all other signatures in a data volume. If an exact block match exists, a byte-by-byte comparison is done for all the bytes in the block, and the duplicate block is discarded and its disk space is reclaimed.
You can configure deduplication operations to run automatically or according to a schedule. You can deduplicate new and existing data, or only new data. You cannot enable deduplication on the root volume.
Deduplication removes data redundancies, as shown in the following illustration: