Availability Options¶
Azure provides several options to protect your virtual machines from hardware failures, network outages, and data center disasters. Use these mechanisms to meet your application's Service Level Agreement (SLA) requirements.
| Option | SLA | Scope | Protection Against | Cost Impact | When to Use |
|---|---|---|---|---|---|
| Single VM (Premium SSD) | 99.9% | Instance | No built-in redundancy; single-instance SLA only | Base | Dev/Test, low criticality |
| Availability Set | 99.95% | Fault/update domains | Hardware/Update failures | Low | Legacy apps, no zone support |
| Availability Zone | 99.99% | Data Center | Data center failure | Medium | High availability, primary production |
| VMSS | 99.95% - 99.99% | Depends on topology (FD spread or multi-zone) | Large-scale failures | Variable | Auto-scaling workloads |
| Cross-Region (ASR) | Variable | Region | Regional disaster | High | Disaster recovery, business continuity |
graph TD
Start([Start Selection]) --> Scale{Auto-scaling needed?}
Scale -->|Yes| VMSS[VM Scale Sets]
Scale -->|No| Zone{Zone-aware region?}
Zone -->|Yes| AZ[Availability Zones]
Zone -->|No| AS[Availability Sets]
AZ --> DR{Regional redundancy?}
AS --> DR
DR -->|Yes| ASR[Azure Site Recovery]
DR -->|No| End([End Selection])Warning
Availability Sets only protect against failures within a single data center. For protection against data center outages, you must use Availability Zones.