Explanation:
The storage can use Fibre Channel, iSCSI, FCoE, or SAS for shared disk storage, or use locally attached storage with Storage Spaces Direct (S2D).
Box 1: Storage Spaces Direct
* Storage Spaces Direct
Storage Spaces Direct requires 2 and up to 16 Microsoft-approved servers with direct-attached SATA, SAS, NVMe, or persistent memory drives that are physically attached to just one server each. Each server must have at least two solid-state drives, and at least four more drives. The SATA and SAS devices should be behind a host-bus adapter (HBA) and SAS expander.
Box 2: 3
For a single application or service requiring high availability across three availability zones, you need a minimum of three subnets, with one subnet in each availability zone. This setup ensures that if one availability zone experiences an outage, your application can still operate from the remaining availability zones, maintaining its availability and fault tolerance.
Reference:
https://learn.microsoft.com/en-us/azure/azure-sql/virtual-machines/windows/failover-cluster-instance-storage-spaces-direct-manually-configure?
https://learn.microsoft.com/en-us/azure/azure-sql/virtual-machines/windows/performance-guidelines-best-practices-storage
https://learn.microsoft.com/en-us/azure/virtual-machines/disks-enable-ultra-ssd
https://learn.microsoft.com/en-us/azure/azure-sql/virtual-machines/windows/availability-group-manually-configure-tutorial-multi-subnet