Purchasing models, service tiers, and hardware choices
After you have an idea of which deployment option is best for your requirements, you need to determine the purchasing model, service tier, and hardware. This unit provides an overview of the purchasing options and when to choose them.
The Azure SQL purchasing model provides two options:
- Purchase based on virtual cores (vCore-based)
- Purchase based on database transaction units (DTU-based)
The DTU model isn't available in Azure SQL Managed Instance.
We recommend the vCore-based model, because it allows you to independently select compute and storage resources. The DTU-based model is a bundled measure of compute, storage, and I/O resources.
In the vCore model, you pay for:
- Compute resources: The service tier plus the number of vCores and the amount of memory plus the generation of hardware.
- Data and log storage: The type and amount of data and log storage.
- Backup storage location: Read-access geo-redundant storage (RA-GRS), zone-redundant storage (ZRS), or locally redundant storage (LRS).
The vCore model also allows you to use Azure Hybrid Benefit for SQL Server and/or reserved capacity (pay in advance) to save money. Neither of these options is available in the DTU model.
This module focuses on the vCore purchasing model.
Next, you need to choose a service tier for performance and availability. We recommend you start with the General Purpose tier and adjust as needed. Three tiers are available in the vCore model:
- General Purpose: Suitable for most business workloads. Offers budget-oriented, balanced, and scalable compute and storage options.
- Business Critical: Suitable for business applications with low-latency response requirements. Offers the highest resilience to failures by using several isolated replicas. This tier is the only one that can use in-memory OLTP (online transactional processing) to improve performance.
- Hyperscale: Suitable for business workloads with highly scalable storage (100 TB+) and read-scale requirements. From a performance and cost perspective, this tier falls between General Purpose and Business Critical. Hyperscale is currently available only for single databases in Azure SQL Database.
If you choose the General Purpose tier and the vCore-based model, you have another decision to make regarding the compute tier that you pay for:
- Provisioned compute is meant for more regular usage patterns with higher average compute utilization over time, or for multiple databases that use elastic pools. Provisioned compute provides a fixed amount of resources over time to ensure optimal performance, and is billed for those resources regardless of usage. In provisioned compute, you need to manage the sizing of compute resources for your workload.
- Serverless compute is meant for intermittent, unpredictable usage with lower average compute utilization over time. Serverless provides automatic compute scaling to simplify performance management, and is billed only for the amount of compute used. Serverless also supports automatic pausing and resuming to help further price optimize. When your database is paused, you pay only for storage.
The default hardware generation at this time is referred to as standard-series hardware, formerly known as Gen5. Premium-series hardware provides the latest and greatest premium storage and compute hardware.
If you choose General Purpose within SQL Database and want to use the serverless compute tier, Gen5 hardware is currently the only option. It can currently scale up to 40 vCores.
The purchasing model, service tier, and hardware selections you make have a significant impact on the performance, availability, and cost of your deployment.