Azure SQL Database Architecture
Understanding the architecture of Azure SQL Database is crucial for optimizing performance, ensuring availability, and managing costs effectively. Azure SQL Database is a fully managed Platform as a Service (PaaS) offering that handles most database management functions like upgrading, patching, and backups without user intervention.
Service vs. Data Layer
Azure SQL Database architecture is a logical separation of the service layer and the data layer.
Key Components
Compute and Storage Units
Azure SQL Database operates on a distributed architecture. Compute and storage are decoupled. Each logical server hosts one or more logical databases. The underlying infrastructure is managed by Azure and uses distributed components:
- Compute Nodes: These are responsible for executing queries and processing transactions. They run on virtualized compute resources.
- Storage Nodes: These store the actual database files. Data is replicated across multiple storage nodes for redundancy and availability.
Service Layer Components
The service layer is responsible for:
- Client Connectivity: Handles connections from applications and manages network traffic.
- Query Processing: Parses, optimizes, and executes SQL queries.
- Transaction Management: Ensures ACID compliance for transactions.
- Security and Authentication: Manages user access and permissions.
Data Layer Components
The data layer is responsible for:
- Data Storage: Physically stores database files and indexes.
- Replication and Redundancy: Ensures data durability and availability through replication mechanisms.
- Backup and Recovery: Manages automated backups and facilitates point-in-time restores.
Deployment Models
Azure SQL Database offers different deployment models to suit various needs:
- Single Database: A fully managed database with its own set of resources.
- Elastic Pool: A collection of databases with shared resources, ideal for managing multiple databases with varying usage patterns.
- Managed Instance: A nearly 100% compatible instance of SQL Server, offering greater compatibility with on-premises deployments.
High Availability and Disaster Recovery
Azure SQL Database is designed for high availability. It leverages several mechanisms:
- Replication: Data is automatically replicated to multiple locations for redundancy.
- Automatic Failover: In case of hardware failure or planned maintenance, your database is automatically failed over to a replica with minimal downtime.
- Geo-Replication: Allows you to create readable replicas of your database in different geographic regions for disaster recovery purposes.
Scalability
Azure SQL Database offers elastic scalability, allowing you to adjust compute and storage resources based on demand. You can scale resources up or down with minimal downtime.
For more detailed information, refer to the official Azure SQL Database documentation.