SnapVault operates at the logical level and when data compression is enabled on the source system, the data is uncompressed in memory on the source system before it is backed up.
When data compression is enabled on the source volume, no bandwidth savings are achieved over the network because the data is uncompressed on the source volume before it is sent for replication. If inline compression is enabled on the destination volume, the data is compressed inline at the destination before it is written to the disk. If inline compression is not enabled on the destination volume, you must manually compress the data after the SnapVault transfer is completed to achieve storage space savings in the destination volume.
For more information about inline compression and how data compression works with SnapVault, see the Data ONTAP Storage Management Guide for 7-Mode.