Is the compute power and metrics for SQL Managed Instance shared across all the databases?

Question

We are trying to analyze and monitor our Azure SQL Managed Instance and identify if we could scale down some resources for cost saving purposes.

If there are multiple databases under the SQL Managed Instance, is there a way to check the individual metrics for each database? Is it possible to scale down selected database only and not the whole SQL MI?

How does SQL MI work? Is it like pooled? Is the compute power and storage shared across all the databases? It seems like when provisioning or creating a new database, we cannot specify the cores.

Answer 1

Hi Junick,

So the Azure SQL Managed Instance (SQL MI) offers a blend of the cloud's scalability and managed services with the familiarity and capabilities of an on-premises SQL Server. Understanding how resources are allocated, used, and can be optimized in SQL MI is essential for managing costs and performance. Here's a breakdown of your queries regarding monitoring, scaling, and how SQL MI works, especially in the context of handling multiple databases:

How SQL Managed Instance Works

• Resource Pooling: Azure SQL Managed Instance operates on a pooled resource model. This means that the compute (vCores), memory, and storage are provisioned at the managed instance level rather than for individual databases. All databases within a single managed instance share these resources. This model is designed to offer flexibility, high availability, and simplified management, akin to managing a cluster of databases in a traditional SQL Server environment but with the benefits of a fully managed service.
• Provisioning Resources: When you create an Azure SQL Managed Instance, you specify the number of cores, the amount of storage, and the service tier. These resources are allocated to the entire instance rather than to individual databases. Consequently, when you add a new database to the instance, you don't specify resources like cores or storage specifically for that database; it simply becomes part of the managed instance and shares the instance's resources.

Monitoring Individual Databases

• Metrics and Monitoring: Azure provides tools for monitoring the performance and resource utilization of SQL Managed Instances and their databases. You can use Azure Monitor and Azure SQL Analytics (in Azure Monitor) to view metrics at both the instance and database levels. This includes metrics like CPU utilization, IO, and memory usage, which can help identify databases with high resource consumption.
• Query Performance Insights: This feature allows you to monitor and identify high-impact queries that could be optimized to reduce resource consumption. It can provide insights at the database level, helping you understand the workload characteristics of individual databases.

Scaling Down Resources

• Scaling Databases: Since resources are allocated at the managed instance level, it's not possible to scale down resources for an individual database within a SQL Managed Instance. If you identify that a specific database requires fewer resources, the primary option for scaling down would involve moving that database to a different managed instance with lower overall resources or considering Azure SQL Database (single database model) where you can allocate specific resources per database.
• Scaling Managed Instances: If overall analysis shows that your managed instance's databases collectively require fewer resources, you can scale down the entire SQL Managed Instance. This process involves adjusting the vCore count or the service tier to better align with your actual resource needs, thus potentially lowering costs.

Cost Optimization Strategies

1. Performance Tuning: Regularly review and optimize your SQL queries and database indexing strategies to ensure efficient use of resources.
2. Elastic Pools: For scenarios where individual databases have variable and unpredictable resource consumption, consider using Azure SQL Database elastic pools, which allow databases to share a set of resources dynamically.
3. Managed Instance Scaling: Scale your SQL Managed Instance based on actual usage patterns. Azure's flexibility allows you to adjust resources as needed, although this applies to the instance as a whole.

So in summary, while SQL Managed Instance offers a pooled resource model that simplifies management and provides flexibility, it requires a different approach to cost optimization compared to managing resources for individual databases. Leveraging Azure's monitoring tools and considering architecture adjustments based on usage patterns are key to optimizing costs and performance in this environment. I hope this answers your queries? If you have any questions please let me know.