Azure SQL Database Architecture
This document provides an in-depth look at the architecture of Azure SQL Database, explaining how it is built on a distributed platform and leverages the capabilities of Azure SQL Managed Instance and SQL Server.
Core Components and Concepts
Azure SQL Database is a fully managed Platform as a Service (PaaS) database engine that handles most database management functions such as upgrading, patching, backups, and high availability without user involvement. It is built on the same engine as SQL Server but runs on a distributed platform.
The Shared Responsibility Model
In Azure SQL Database, Microsoft is responsible for the underlying infrastructure, operating system, and database engine patching and updates. You, as the customer, are responsible for your data and the access to it. This model simplifies database management and allows you to focus on your applications.
The Scale-Out Architecture
Azure SQL Database is designed for massive scale and high availability. It utilizes a sophisticated distributed architecture that separates compute and storage, enabling independent scaling and resilience. Key elements include:
- Control Plane: Manages metadata, authentication, and resource provisioning.
- Data Plane: Hosts the actual database engine and data. This is where the compute nodes reside.
- Gateway: Routes client connections to the appropriate compute node.
Logical Architecture Diagram
A simplified view of the Azure SQL Database architecture:
Note: This is a conceptual diagram. The actual implementation involves numerous redundant systems and services.
Understanding Compute and Storage Separation
One of the fundamental architectural advantages of Azure SQL Database is the separation of compute and storage. This allows for:
- Independent Scaling: You can scale compute resources (CPU, memory) independently of storage capacity, and vice versa.
- High Availability: Compute nodes are stateless. If a compute node fails, the database can be quickly failed over to another available compute node with minimal downtime.
- Cost Efficiency: You pay for the resources you consume, optimizing costs.
Deployment Options
Azure SQL Database offers several deployment options to cater to different needs:
- Single Database: A self-contained database with its own set of resources managed via a logical server.
- Elastic Pool: A collection of databases with shared resources, ideal for SaaS applications with varying usage patterns.
- Azure SQL Managed Instance: A near 100% compatible version of SQL Server, ideal for migrating existing SQL Server workloads to the cloud.
Key Architectural Layers
The Azure SQL Database engine is built on a robust foundation:
- Database Engine: The core of SQL Server, optimized for the cloud.
- Storage Layer: Leverages Azure Storage for highly available and durable data storage.
- Networking Layer: Provides secure and efficient connectivity.
- Management Layer: Handles provisioning, scaling, monitoring, and high availability.
High Availability and Disaster Recovery
Azure SQL Database offers built-in high availability and disaster recovery capabilities:
- Availability Zones: Spanning availability zones for maximum resilience against datacenter failures.
- Geo-Replication: Asynchronous replication of databases to different regions for disaster recovery.
- Automatic Backups: Regular automated backups stored in geo-redundant storage.
Performance and Scalability
The distributed nature of Azure SQL Database allows for seamless scaling of both performance and storage. You can choose from various service tiers (General Purpose, Business Critical, Hyperscale) and compute sizes to match your workload requirements.