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Deduplication with volume SnapMirror

Starting with Data ONTAP 8.1, two copies of the deduplication metadata are maintained for a FlexVol volume. One copy of the metadata resides in the volume while the other copy resides in the aggregate.

When replicating data using volume SnapMirror, the deduplication metadata for the volume is replicated along with the volume. The data in the volume is usable both on the source and the destination.
Note: When configuring volume SnapMirror and deduplication, you should ensure that deduplication and volume SnapMirror operations do not run at the same time. You should start volume SnapMirror transfer of a deduplicated volume after the deduplication operation is complete. This prevents any impact to the replication performance while deduplication is in progress and sending of undeduplicated data and additional temporary deduplication metadata files over the network.
To achieve maximum space savings on the destination volume, you must scan the entire file system to re-create the deduplication metadata for the destination volume. Use the sis start -s command to do so.
Note: The destination volume is accessible for read-write operations when the deduplication scan is in progress.

If you use the sis start command without the -s option, the potential for space savings on the destination volume is reduced because only the new data written to the volume is scanned for deduplication.

For more information about deduplication, see the Data ONTAP Storage Management Guide for 7-Mode.