Using the Azure SQL Database DTU Calculator

Over the past year I’ve been teaching and helping clients with Azure SQL Database. One of the most common questions I’m asked is, “What size tier do I need for my database?” I instinctively refer them to the DTU Calculator. This is a free tool that you can use to capture local instance metrics and upload to a website for an estimation of the service tier needed. The DTU calculator captures data on processor, disk reads and writes, and log bytes flushed.

Something to take into consideration about the DTU Calculator is that it collects the metrics for the entire instance. If you are looking to migrate a single database from an instance, then those metrics will be skewed. Depending on your situation, this may be fine, you’d know that the database in question would fit within the tier recommended by the DTU Calculator. If this is not acceptable, another option would be to isolate the database to it’s own instance, and then run the DTU Calculator against that instance.

Justin Henriksen, the creator of the DTU Calculator suggests that you could use SQL Server DMVs to isolate a database, but I personally have not tried this.

The DTU Calculator is offered in an executable with a configuration file and a PowerShell script. The two items I typically change are the location and name of my output file and the duration the script runs. The duration defaults to 3600 seconds, but when I’m conducting demos, I usually reduce this to 60 seconds. In the real world, I run the process for 1 hour increments, and continuously throughout the day so I get a full picture of the workload. I was excited to see the addition of the executable command line tool rather than just the PowerShell option.

If you’re looking to migrate multiple databases to Azure SQL Database, then an Elastic Database Pool is most likely a better option for you instead of managing multiple individual Azure SQL Database tiers. With an Elastic Database Pool, you’ll have a pool of eDTUs that each database can pull from (individual database limitation differences between Standard and Premium pools).

If you are considering Azure SQL Database, check out the DTU Calculator and if you need assistance migrating from On Premises to Azure or Azure SQL Database, let us know.

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