How to choose right threshold value for DCU percentage metric alert?

Question

I have created a single instance of azure sql database with DTU-based purchase model. I am trying to setup some metric alerts for this database so once I use this Db for some application I can have better picture of how DTU's are actually being used, how many / much DTU's I will need etc. This information will help me to Configure right Pricing tier for this database.

Pricing tier info

Answer 1

Before you set the alerts, you should first use the Metric to monitor databases using the Azure portal. In the Azure portal, you can monitor an individual databases utilization by selecting your database and clicking the Monitoring chart. This brings up a Metric window that you can change by clicking the Edit chart button. Add the following metrics:

• CPU percentage
• DTU percentage
• Data IO percentage
• Database size percentage

You can also configure alerts on the performance metrics. Click the Add alert button in the Metric window. Follow the wizard to configure your alert. You have the option to alert if the metrics exceed a certain threshold or if the metric falls below a certain threshold.

For example, if you expect the workload on your database to grow, you can choose to configure an email alert whenever your database reaches 80% on any of the performance metrics. You can use this as an early warning to figure out when you might have to switch to the next highest compute size.

The performance metrics can also help you determine if you are able to downgrade to a lower compute size. Assume you are using a Standard S2 database and all performance metrics show that the database on average does not use more than 10% at any given time. It is likely that the database will work well in Standard S1. However, be aware of workloads that spike or fluctuate before making the decision to move to a lower compute size.

Azure gives you the examples are setting the threshold value of the DTU/CPU metric 80%. You also can get this in this document: Create an alert rule on a metric with the Azure portal.

So you can reference this value on threshold. If your database CPU or DTU percentage is over 80% or with slow performance for a long time, you should consider to scale up the DTU-based price tier.

Hope this helps.