Azure Resource Manager vs Terraform: What are the differences?

Introduction

In this article, we will discuss the key differences between Azure Resource Manager (ARM) and Terraform. Both ARM and Terraform are widely used Infrastructure as Code (IaC) tools that enable the provisioning and management of cloud resources. However, there are several distinct differences between the two.

1. Management Framework: Azure Resource Manager is a native management framework provided by Microsoft Azure for deploying resources and managing infrastructure. It is tightly integrated with Azure services and provides a unified API and control plane for resource provisioning and orchestration. On the other hand, Terraform is a multi-cloud infrastructure provisioning tool that is independent of any specific cloud provider. It uses a declarative language to define infrastructure configurations and can deploy resources across different cloud platforms, including Azure.

2. Declarative vs. Imperative: Azure Resource Manager uses a declarative approach, where you define the desired state of the infrastructure and let the platform handle the implementation details. You specify the desired configuration in ARM templates, which are JSON files describing the resources and their properties. Terraform, on the other hand, takes an imperative approach. You define the sequence of steps required to reach the desired state, and Terraform handles the execution. It uses a declarative language called HashiCorp Configuration Language (HCL) to define infrastructure configurations.

3. Community and Ecosystem: Azure Resource Manager has a rich ecosystem and a vast collection of pre-built templates and artifacts available in the Azure Marketplace. It also integrates well with other Azure services and tools. Terraform, on the other hand, has an active and growing community with contributions from various cloud providers and users. It has a wide range of community-maintained providers and modules that extend its capabilities beyond just Azure, enabling users to provision and manage resources across different cloud platforms.

4. Versioning and State Management: Azure Resource Manager provides built-in version control for templates, allowing you to track and manage changes over time. It also integrates with Azure DevOps for continuous integration and delivery (CI/CD) pipelines. Terraform, on the other hand, uses its own state management system to keep track of the deployed resources and their dependencies. This state is stored locally by default, but it can also be stored remotely in a backend system, enabling collaboration and sharing of the infrastructure state across a team.

5. Resource Granularity and Customization: Azure Resource Manager allows you to manage resources at a high level of abstraction, such as virtual networks, storage accounts, or virtual machines. It provides a wide range of built-in resource types and properties that can be customized using ARM templates. Terraform, on the other hand, provides more granular control over resources. It supports a broad spectrum of resource types and allows you to define and manage resources with fine-grained configuration options.

6. Vendor Lock-In and Multi-Cloud Support: While Azure Resource Manager is tightly integrated with Azure and provides a seamless experience for managing Azure resources, it may introduce vendor lock-in if you want to switch to a different cloud provider. Terraform, being a multi-cloud tool, offers greater flexibility and portability. It allows you to provision and manage resources across different cloud providers, reducing the risk of vendor lock-in and enabling multi-cloud and hybrid cloud deployments.

In summary, Azure Resource Manager is a native management framework tightly integrated with Azure, providing a unified API for managing Azure resources using declarative ARM templates. Terraform, on the other hand, is an infrastructure provisioning tool that is cloud-agnostic and supports multiple cloud providers using a declarative language called HCL. Terraform offers more granular control, a vibrant community, and multi-cloud support, making it a popular choice for managing infrastructure-as-code across various cloud platforms.