During mirroring operations, de-duplication operations are applied to the mirror volumes. Data stored to a first volume is mirrored to a second volume. The second volume is a virtual volume having a plurality of logical addresses, such that segments of physical storage capacity are allocated for a specified logical address as needed when data is stored to the specified logical address. A de-duplication operation is carried out on the second volume following a split from the first volume. A particular segment of the second volume is identified as having data that is the same as another segment in the second volume or in the same consistency group. A link is created from the particular segment to the other segment and the particular segment is released from the second volume.