Azure SQL Database Architecture Overview
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 monitoring without user involvement. It's built on the SQL Server engine, providing compatibility with on-premises SQL Server.
The architecture is designed for high availability, scalability, and security, leveraging Azure's global infrastructure. Understanding the underlying architecture is crucial for optimizing performance, cost, and reliability.
Conceptual Architecture Diagram
Compute Model
Azure SQL Database offers various compute models to suit different needs:
- Single Database: Provides dedicated compute resources for a single database. Ideal for new cloud applications.
- Elastic Pool: A collection of databases with a shared set of resources. Useful for managing multiple databases with varying usage patterns.
- Managed Instance: A fully managed instance of the SQL Server engine, offering near 100% compatibility with on-premises SQL Server. Suitable for lift-and-shift scenarios.
Each model abstracts the underlying hardware and operating system, allowing you to focus on your data.
Storage Model
Storage in Azure SQL Database is managed by Azure Storage. It uses distributed storage systems that provide high durability and availability.
- Data and log files are stored separately and managed for performance and resilience.
- The storage architecture is optimized for fast I/O operations.
- Different service tiers (General Purpose, Business Critical, Hyperscale) offer varying performance and storage capabilities.
For example, the Hyperscale tier offers independent scaling of compute and storage, with storage sizes up to 100TB.
Networking
Azure SQL Database can be accessed securely over the network. Key networking features include:
- Private Endpoint: Provides a private IP address from your virtual network, ensuring traffic stays within your network.
- Service Endpoint: Restricts network access to Azure SQL Database resources from a specific subnet of your virtual network.
- Firewall Rules: Control access to your Azure SQL Database server by specifying allowed IP address ranges.
Secure network configurations are essential to protect your data.
High Availability & Disaster Recovery
Azure SQL Database is designed with built-in high availability and disaster recovery capabilities.
Disaster Recovery (DR): Protects your data against large-scale outages. Options include:
- Active Geo-Replication: Allows you to create readable secondary databases in different Azure regions.
- Auto-Failover Groups: Provides automatic failover capabilities for a group of databases.
- Point-in-time restore (PITR) and Long-term backup retention (LTR) are also critical DR components.
Scalability Options
Azure SQL Database offers flexible scalability to meet changing demands.
- Vertical Scaling: Increase or decrease the DTUs (Database Transaction Units) or vCores allocated to your database or elastic pool.
- Horizontal Scaling: For single databases, you can scale up/down. For read-intensive workloads, consider readable secondary replicas with geo-replication.
The Hyperscale tier allows for independent scaling of compute and storage, offering even greater flexibility.
Security Features
Security is a top priority in Azure SQL Database. It incorporates a multi-layered approach:
- Network Security: Firewalls, Private Endpoints, Service Endpoints.
- Authentication: SQL authentication and Azure Active Directory (Azure AD) authentication.
- Authorization: Role-based access control (RBAC).
- Data Protection: Transparent Data Encryption (TDE), Always Encrypted, Dynamic Data Masking, Row-Level Security.
- Threat Protection: Advanced Threat Protection offers security alerts and vulnerability assessments.
Leveraging these features is crucial for maintaining a secure database environment.