For Business Continuity Clustering, a shared disk storage system is required for each peer cluster in the business continuity cluster. See Shared Disk Configuration Requirements
in the OES 2018 SP3: OES Cluster Services for Linux Administration Guide.
Each peer cluster contains shared disks for its own resources plus shared disks for resources in peer clusters that are assigned to fail over to it. You must mirror the data between the sites as described in Section 4.13, Mirroring Shared Disk Systems between Peer Clusters.