The requirements for immediate failover (disaster recovery) and long-term retention (backup/archive) are best met by using two distinct, specialized SnapMirror policies. A mirror-latest relationship provides an up-to-date copy of the data on a secondary site, enabling a quick cutover for DR. A separate vault relationship, typically from the same source to a third destination (or from the DR destination), replicates and retains a history of snapshots for long-term archival and granular recovery. This "fan-out" or "cascade" architecture is a standard NetApp best practice for unified data protection.

B. A single vault policy is asynchronous and cannot achieve an RPO of 0. It is designed for retention, not immediate failover.

C. SnapMirror Sync provides immediate failover (RPO=0) but does not inherently retain a long history of snapshots for archival purposes.

D. SnapLock is a WORM feature for data immutability and compliance; it does not provide replication or failover capabilities for disaster recovery.

1. NetApp. (2023). TR-4015: ONTAP Data Protection Power Guide. Section: "Unified data protection," pp. 14-15. This section describes combining SnapMirror and SnapVault (now unified under SnapMirror policies) to achieve both DR and backup, often using a fan-out topology with separate relationships.

2. NetApp. (2023). ONTAP 9 Data protection administration guide. Section: "Data protection scenarios". The documentation illustrates configurations where different SnapMirror relationships are used from a single source to meet multiple objectives like DR and backup.