How volume SnapMirror works with data compression

Because volume SnapMirror operates at the physical block level, when data compression is enabled on the source storage system, the data remains compressed when it is replicated to the destination storage system. This operation can significantly reduce the amount of required network bandwidth during replication.

When using volume SnapMirror with data compression, you must observe the following guidelines:

• For SnapMirror transfer to occur, the source and destination volumes must be contained in 64-bit aggregates and the destination storage system must be running the same or later version of Data ONTAP.

  For example, if the source storage system is running on Data ONTAP 8.0.1, then the destination storage system must be running on Data ONTAP 8.0.1 or later. If the source storage system is running on Data ONTAP 8.1, then the destination storage system must be running on Data ONTAP 8.1 or later.

• You can enable, run, and manage data compression only from the primary storage system.

  However, the FlexVol volume in the secondary storage system inherits all the data compression attributes and storage savings through the volume SnapMirror transfer.

• If you plan to compress existing data in the disk with the -s option on a FlexVol volume that has data blocks locked in Snapshot copies and has existing volume SnapMirror relationships, then this operation might result in a large transfer of data blocks.

  The data compression operation rewrites data as new compressed blocks and these blocks are transferred in the next incremental transfer.

For more information about volume SnapMirror, see the Data ONTAP Data Protection Online Backup and Recovery Guide for 7-Mode.