diff --git a/internal/volume/volumes_information.go b/internal/volume/volumes_information.go
index cec2922d9..50b614caf 100644
--- a/internal/volume/volumes_information.go
+++ b/internal/volume/volumes_information.go
@@ -181,6 +181,9 @@ type SnapshotDataMovementInfo struct {
 	// incremental and must stay distinguishable from "unknown".
 	IncrementalSize *int64 `json:"incrementalSize,omitempty"`
 
+	// The size of source volume, for backup only
+	SourceSize int64 `json:"sourceSize,omitempty"`
+
 	// The DataUpload's Status.Phase value
 	Phase velerov2alpha1.DataUploadPhase
 }
diff --git a/pkg/backup/backup.go b/pkg/backup/backup.go
index 038b85cc1..ce2addaec 100644
--- a/pkg/backup/backup.go
+++ b/pkg/backup/backup.go
@@ -1325,6 +1325,7 @@ func updateVolumeInfos(
 				volumeInfos[index].SnapshotDataMovementInfo.RetainedSnapshot = dataUpload.Spec.CSISnapshot.VolumeSnapshot
 				volumeInfos[index].SnapshotDataMovementInfo.Size = dataUpload.Status.Progress.TotalBytes
 				volumeInfos[index].SnapshotDataMovementInfo.IncrementalSize = dataUpload.Status.IncrementalBytes
+				volumeInfos[index].SnapshotDataMovementInfo.SourceSize = dataUpload.Status.SourceSize
 				volumeInfos[index].SnapshotDataMovementInfo.Phase = dataUpload.Status.Phase
 
 				if dataUpload.Status.Phase == velerov2alpha1.DataUploadPhaseCompleted {