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Performance Tiers for Azure SQL Database

Azure SQL Database offers a range of performance tiers designed to meet diverse application workloads and budget requirements. Understanding these tiers is crucial for optimizing your database's performance and cost-effectiveness.

Understanding Performance Tiers

Azure SQL Database performance is measured by metrics like DTUs (Database Transaction Units) or vCore. The performance tiers categorize available resources, primarily focusing on:

• Compute: CPU, memory.
• I/O: Read and write throughput, latency.

DTU-based Purchase Model

The DTU model offers a bundled measure of these resources in a simple, blended value. It's a good starting point for understanding performance.

DTU Tiers:

• Basic: Suitable for development, testing, and small, infrequently used applications. Offers limited resources.
• Standard: A good balance of performance and cost for most general-purpose applications. Offers more resources than Basic.
• Premium: Designed for mission-critical applications with high I/O requirements and the need for faster performance. Offers the highest DTU availability.

Here's a general overview of what DTUs represent:

• CPU power
• Memory
• I/O bandwidth
• I/O rate

vCore-based Purchase Model

The vCore model provides more transparency and control over your compute resources. You can independently scale compute and storage, and choose hardware generations.

vCore Tiers:

• General Purpose: Offers a balanced combination of compute and storage with scalable I/O throughput. Ideal for most business applications.
• Business Critical: Provides the highest level of performance and availability, with the fastest I/O, low latency, and built-in high availability. Suitable for mission-critical applications.
• Hyperscale: Designed for customers with large databases and high transaction rates. It offers independent scaling of compute and storage, up to 100TB.

Key Differentiators

Feature	DTU (Basic/Standard)	DTU (Premium)	vCore (General Purpose)	vCore (Business Critical)	vCore (Hyperscale)
Compute Unit	DTU	DTU	vCore	vCore	vCore
Primary Focus	Balanced cost/performance	High performance, low latency I/O	Balanced cost/performance, scalable I/O	Max performance, low latency I/O, HA	Large databases, high throughput
Resource Scaling	Bundled (DTU)	Bundled (DTU)	Independent Compute/Storage, scalable I/O	Independent Compute/Storage, scalable I/O	Independent Compute/Storage, scalable I/O
High Availability	Standard: Basic HA Premium: Enhanced HA	Enhanced HA	Standard HA	Built-in HA (multiple replicas)	Configurable replicas
Storage Options	Fixed per tier	Fixed per tier	Scalable, independent of compute	Scalable, independent of compute	Up to 100TB, independent of compute

Choosing the Right Tier

Consider the following factors when selecting a performance tier:

• Workload requirements: Analyze your application's CPU, memory, and I/O needs.
• Performance expectations: What are your latency and throughput targets?
• Budget constraints: Balance performance needs with cost considerations.
• Availability requirements: Do you need built-in high availability or disaster recovery features?

For most typical applications, the Standard (DTU) or General Purpose (vCore) tiers offer a good starting point. For demanding, mission-critical applications requiring maximum performance and availability, Premium (DTU) or Business Critical (vCore) are recommended. If you manage very large databases or require extreme scalability, Hyperscale is the ideal choice.

Further Reading

• Resource Limits
• Performance Tuning and Optimization