Azure SQL Database service tiers

In this azure tutorial, we will discuss Azure SQL Database service tiers. Apart from this, we will also discuss on the below topics

  • How to Choose the Right Service Tier
  • Is Azure SQL database free
  • Azure dtu calculator

Azure SQL Database service tiers

There are two service tires for Azure SQL Database and SQL Managed Instance

  • General Purpose
  • Business Critical
Azure SQL Database tiers

General Purpose

The General Purpose service tier architecture is based on the separation of compute and Azure storage.

General Purpose service tier architecture

This service model guarantees no data loss in case of infrastructure failure.

There are two layers in case of General Purpose service tier

1- A stateless compute layer that is running the sqlservr.exe process

2- A stateful data layer with database files that are stored in Azure Blob storage

In case of infrastructure failure, Azure Service Fabric will move the stateless process to another stateless compute node. There are different set of buffer nodes available to run the new compute service in case of any failure happens

This process guarantees 99.99% availability.

Business Critical

Business Critical service tier is based on a cluster of database engine processes.

This architecture model will make sure that there is always a quorum of available database engine nodes and has very little performance impact on your workload even during maintenance activities.

Business Critical service tiers are designed for very intensive workload support even in case of any ongoing maintenance operations.

In this model, compute and storage is integrated on the single node and replication of compute and storage deployed to a four-node cluster.

Business critical service tier architecture

 In this case, the primary node pushes the changes to the secondary nodes in order to make sure that the data is available on secondary replicas if by chance the primary node fails for any infrastructure failure.

How to Choose the Right Service Tier

When you are creating an Azure SQL database, the first thing that will come to our mind is which service tier to choose.

This is very common that everyone will look for the service tier one that will be very cheap.

To be honest, choosing the right Azure SQL database service tier is not a very straightforward task.

This depends on the number of factors like what is your budget?, Do you have any special requirement for your data?, Size of your data, Do you want dedicated professionals and administration? etc

This is a common fact that the more you pay the more features you will get in your service tier.

Few things are there to keep in mind is that before selecting the service tier, you need to think of what is the maximum size allowed and weather your data can fit there or not?, What is the backup retention period and weather that satisfies as per your business needs?

One more important thing you need to consider is the performance stuff before choosing the right service tier.

The service tier has two main concepts

  • SQL Database Edition
  • Database Throughput Units (DTU)

SQL Database Edition

Basically, there are three types of SQL editions are there

  • Basic
  • Standard
  • Premium

Each editions have there own set of features and limitations.

Normally, the Premium version has more features compared to standard and basic versions and you need to pay more if you are going with the premium version.

All these three edition supports less than or equals to 2 GB of data. Standard and premium versions support starting from 2 GB up to 250 GB of data. Only premium version supports 250 GB to 1 TB of data.

Database Throughput Units (DTU)

The Database Throughput Units (DTU) is an important factor while deciding the service tier. You should decide how many number of DTUs you want to go with as per your business needs. The number of DTU starts from 5 to 1750.

Another important factor to consider here is to see the business Continuity options. There are different business continuity options available like

Geo-Restore: This option is available in all the editions. This is related to the last daily back up option based on the region.

Standard Geo-Replication: This option is available for the standard and premium editions. You can define a fixed disaster recovery pair.

Active Geo-Replication: This option is available only in the premium edition. This is most powerful business continuity plan.

Point-in-Time restore: Backups are included on this particular continuity option. The retention duration depends on the edition you are selecting for Basic – 7 days back, Standard – 14 days back and for premium – 35 days back.

Performance is another important factor to consider while choosing the service tier for Azure SQL database.

In case of SQL database the horse power is measured with Database Throughput Units (DTU). You can choose in between 5 to 1750 based on your business need.

When you will choose more number of DTU then yon need to pay more in that case. It is directly proportional to the price you need to pay.

Azure dtu calculator

To calculate the exact number of the DTUs you need, you can use the DTU calculator. What You need to do is you need to download a PowerShell script on the above site, and then you run it in the server where your database is present. immediately after running this script, you will get the following data in a CSV file

  • Processor – % Processor Time
  • Logical Disk – Disk Reads/sec
  • Logical Disk – Disk Writes/sec
  • Database – Log Bytes Flushed/sec

Enter the number of cores and upload the CSV file with the above data. Click the Calculate button to view your recommended Service Tier/Performance Level and DTUs.

Azure dtu calculator

Is Azure SQL database free

Yes, you can create a free account in Azure where you will get the below benefits.

  • You will get ₹13,300 credit for free for a period of 30 days.
  • 12-month free access to Azure SQL Database.
  • Free access to 25 + other services.

To create a free account to get all the above benefit, follow my article How to Create Azure Free Account (Step by Step tutorial)

You may like following Azure tutorials


In this Azure tutorial, We discussed

  • Azure SQL Database tiers
  • How to Choose the Right Service Tier
  • Is Azure SQL database free
  • Azure dtu calculator

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