A vSAN Stretched Cluster requires both compute placement control and storage placement control. To place virtual machines in the appropriate site, the administrator must create VM/Host groups for the two sites. This allows DRS to understand which hosts belong to the preferred site and which hosts belong to the secondary site, and it allows VM-to-host affinity rules to be created for initial and ongoing placement. The administrator must also create a storage policy for each site or site placement requirement. vSAN stretched-cluster storage policies control site disaster tolerance and data locality, including whether objects are mirrored across sites or kept on the preferred or secondary site. VM folders do not control runtime or storage placement. A VM/Host group "across the two sites" is not correct because site separation must be explicitly modeled. Simply placing a VM into a DRS group is not enough unless the site groups and policies already exist. Reference topics: vSAN Stretched Cluster Design Considerations, DRS Host Groups, VM Groups, VM-Host Rules, vSAN Storage Policy Site Locality.

Explanation:
LUN Masking = A security process performed on the storage array by which specific storage components are hidden to prevent unauthorized access to data; Datastore Cluster = A collection of shared resources with a shared management interface that enables resource allocation policies; SAN Fabric = A dedicated high-performance network infrastructure for storage devices; Datastore = A manageable storage entity used as a repository for Virtual Machine files including log files, scripts, configuration files and virtual disks; Host Bus Adapter (HBA) = Added to an ESX host server to allow the host access to the dedicated storage area network; Zoning = A security process completed on the Storage Area Network to ensure only certain devices can communicate with each other.
These definitions describe the core components of a Fibre Channel SAN design in a VCF Workload Domain. LUN masking is performed on the storage array and controls which hosts can see specific LUNs, preventing unauthorized access to storage. A datastore cluster is a collection of datastores managed as a shared resource pool, allowing placement and balancing policies through Storage DRS. A SAN fabric is the dedicated high-performance network that interconnects ESX hosts, Fibre Channel switches, and storage arrays. A datastore is the vSphere logical storage container where VM configuration files, virtual disks, logs, and related files reside. A Host Bus Adapter is the physical or virtual adapter in the ESX host that connects the host to the Fibre Channel storage area network.
Zoning is performed on the Fibre Channel fabric and controls which initiators and targets can communicate. Together, zoning and LUN masking provide layered access control, while datastores and datastore clusters provide the vSphere consumption model. Reference topics: Fibre Channel SAN Concepts, SAN Fabric, Zoning, LUN Masking, VMFS Datastores, Datastore Clusters.

vSAN Stretched Clusters meet the availability-zone requirement by extending a single logical vSAN cluster across two availability zones and using a witness for quorum. This provides rapid recovery from a site or availability-zone failure because workloads remain protected by the stretched topology and vSAN site-failure tolerance. vSAN Storage Cluster addresses the need for scalable, high-performance storage that can grow independently as application capacity requirements increase. In VCF 9.0, a vSAN Storage Cluster is based on vSAN ESA and provides disaggregated storage to vSAN compute or HCI clusters. This design supports storage-dense NVMe-based nodes, high IOPS, low latency, independent capacity scaling, and centralized storage services. Encryption at rest and in transit are native vSAN capabilities that can be enabled on the vSAN-backed storage architecture. vSAN File Service is for file shares, and vSAN iSCSI Target Service is for presenting block LUNs to external initiators; neither is required by the stated application-storage design. vSAN Data Protection is valuable for snapshots and recovery points, but the core architecture requirements are best satisfied by stretched site resilience plus scalable vSAN storage clustering. Reference topics: vSAN Storage Cluster, vSAN Stretched Cluster, vSAN ESA, vSAN Encryption.