Hello Darren Gourley,
Enabling zone redundancy on your Azure SQL Database in East US with a serverless tier isn't possible because the serverless compute model doesn't support it—zone redundancy requires provisioned compute to distribute replicas across availability zones, while serverless uses a dynamic, on-demand model that lacks fixed zonal placement. The "Yes" toggle is greyed out or absent in the portal due to this incompatibility; you'll need to migrate to a provisioned General Purpose or Business Critical tier to enable it. Here's a quick path forward.
Why It's Not Available
Serverless Limitations: Serverless databases (vCore or DTU) prioritize auto-scaling and pause/resume for cost savings but can't guarantee zonal redundancy, as resources aren't pinned to specific zones. East US supports zone redundancy only on provisioned tiers in zones 1-3.
Requirements Check: Your region (East US) is supported, but the compute model blocks it. No errors in setup—just a feature mismatch.
Steps to Enable Zone Redundancy
Migrate to Provisioned Tier: In the Azure portal, go to your SQL Database > Compute + storage (under Settings).
Select Configure > Change tier to General Purpose (or Business Critical for higher resilience).
Choose **Provisioned** compute (e.g., 2 vCores), enable **Zone redundancy** toggle (now available), and apply. Downtime is minimal (~5-10 minutes for small DBs).
CLI alternative: `az sql db update --resource-group <rg> --server <server> --name <db> --zone-redundant Yes --license-type BasePrice --max-size 100GB --compute-model Provisioned --family Gen5 --sku-name GP_Gen5_2 --edition GeneralPurpose`.
**Verify and Test**: Post-update, check **Overview** > **Zone redundancy: Enabled**. Run a failover test via **Tasks** > **Failover** to confirm HA.
**Cost Note**: Provisioned starts ~$0.50/hour (Gen5, 2 vCores); monitor via Cost Management to avoid surprises compared to serverless.
If you must stick with serverless, use geo-replication for redundancy instead (DB > Geo-replication > Add secondary in another region). For larger setups, consider Hyperscale if scale is key.
Best Regards,
Jerald Felix