Comparison of GCR (Google), ECR (Amazon), and ACR (Azure)

Introduction 

Cloud-based applications use containers to make software deployment easier and more scalable. To store and manage these containers, we need container registries. This blog compares three popular container registries: Google Container Registry  (GCR), Amazon Elastic Container Registry (ECR), and Azure Container Registry (ACR), helping you decide the best fit for your needs. 

1. Google Container Registry (GCR) 

Overview

GCR is Google Cloud’s private container registry, designed for secure and scalable storage of Docker images. It works well with Google’s cloud services. 

Key Features 

• Geo-Redundancy: GCR offers geo-redundancy by default, ensuring high availability and low latency. 
• Seamless Integration with GCP: Works seamlessly with Kubernetes (GKE), Compute Engine, and Cloud Build. 
• IAM Access Control: Uses Google Cloud’s Identity and Access Management (IAM) for security. 
• Vulnerability Scanning: GCR includes built-in image vulnerability scanning to identify and mitigate security risks. 
• Private Networking: Supports private access through Google’s Virtual Private Cloud (VPC), ensuring secure image access. 
• Lifecycle Management: Allows users to define lifecycle policies for automatic cleanup of older or unused images. 

Advantages 

• Automatic geo-redundancy ensures high availability without manual setup. 
• Strong integration with Google Cloud services makes it ideal for GCP-based deployments. 
• Built-in vulnerability scanning enhances security. 

Use Cases 

• Businesses using Google Cloud. 
• Companies needing multiple data regions for better performance. 

2. Amazon Elastic Container Registry (ECR) 

Overview 

ECR is AWS’s fully managed container registry, making it easy to store and deploy Docker images. It integrates well with AWS services. 

Key Features 

• Regional Availability: ECR is region-specific, but it supports cross-region replication for global deployments. 
• Deep AWS Integration: Works well with Amazon ECS, EKS, and Lambda. 
• IAM Security: Uses AWS IAM for fine-grained access control. 
• Immutable Image Tags: Ensures image integrity by preventing overwriting of tags. 
• Image Scanning: Provides image vulnerability scanning using Amazon Inspector. 
• Encryption: Images are encrypted both at rest and in transit using AWS-managed or customer-managed keys. 
• Lifecycle Policies: Allows automatic deletion of old or untagged images to manage storage costs. 

Advantages 

• Works best for AWS-based applications. 
• Supports automated image management. 
• High security with IAM-based access control and encryption. 

Use Cases 

• Businesses using AWS services. 
• Companies needing automated image updates and strong security. 

3. Azure Container Registry (ACR) 

Overview 

ACR is Microsoft Azure’s managed container registry, offering seamless integration with Azure services and advanced automation features. 

Key Features 

• Geo-Replication: Allows easy access to images from multiple locations. 
• Azure AD Integration: Uses Azure Active Directory for authentication and role-based access control. 
• Task Automation: Automates image builds, tests, and deployments. 
• Content Trust: Supports Docker Content Trust (DCT) for ensuring the integrity of images by enforcing signed images. 
• Vulnerability Scanning: ACR integrates with Microsoft Defender for Cloud to provide vulnerability scanning for container images. 
• Dedicated Pricing Tiers: Offers Basic, Standard, and Premium tiers to accommodate different performance and storage requirements. 

Advantages 

• Comprehensive integration with Azure services like AKS and App Services. 
• Geo-replication and task automation enhance global scalability and continuous deployment. 
• Flexible pricing tiers allow users to choose based on their budget and performance needs. 

Use Cases 

• Organizations heavily invested in Azure. 
• Applications requiring global scalability and automated image management. 
   

Feature Comparison Table 

Key Differences at a Glance 

Geo-Redundancy vs. Geo-Replication 

• Geo-Redundancy automatically stores data in multiple geographically separated locations for high availability and disaster recovery. No manual setup is needed. 
• Geo-Replication requires manual configuration to copy data across selected regions, usually to optimise performance by keeping data closer to users. 

Manual Cross-Region Replication vs. Geo-Replication 

• Manual Cross-Region Replication (ECR) requires users to select target regions and configure replication manually. 
• Geo-Replication (ACR) allows automatic replication across multiple regions after an initial setup. Once enabled, images pushed to one region are automatically available in all configured regions. 

Automated Builds: GCR & ECR vs. ACR Tasks 

• GCR & ECR only store images; they do not build them. Users must rely on external CI/CD tools like Google Cloud Build (GCR) or AWS CodeBuild (ECR) to create images. 
• ACR Tasks automates image building when code changes. It uses webhook-based triggers, allowing instant builds when a new commit is pushed or a base image is updated. 

Can We Use ECR with Azure/GCP? 

Technically possible but not recommended. 

• Requires complex authentication setup. 
• Security & IAM management becomes difficult. 
• Increased network latency and data transfer costs. 
• Vendor lock-in: Native registries (ECR, GCR, ACR) integrate better with their own cloud platforms. 
   

Geo-Replication in Azure Container Registry (ACR) 

Benefits: 

• Manage a single registry across multiple regions. 
• Use one image URL across all locations. 
• ACR automatically syncs images, reducing data transfer. 
• Get high availability and resilience to regional outages. 
• Configure regional webhooks for event notifications. 

How to Enable Geo-Replication: 

Geo-replication is a feature of Premium registries. If the registry isn't yet Premium, you can change from Basic and Standard to Premium in the Azure portal 

1. In the Azure Portal, go to your Azure Container Registry.  

2. Click on Replications  

3. You can view a map of available regions. 

4. Blue hexagons represent current replica, Gray hexagons represent Azure regions not yet available for replication. 

5. Select a green hexagon (available region)  

6. And click Create. 

7. To configure additional replicas, select the green hexagons for other regions, then click Create, Repeat for additional replicas. 

8. You can also manage geo-replication using tools including the az acr replication commands in the Azure CLI, 

az acr replication create 

Create a replicated region for an Azure Container Registry. 

az acr replication create --location 
                          --registry 
                          [--name] 
                          [--region-endpoint-enabled {false, true}] 
                          [--resource-group] 
                          [--tags] 
                          [--zone-redundancy {Disabled, Enabled}] 

Examples; 

1. Create a replicated region for an Azure Container Registry. 

az acr replication create -r myregistry -l westus 

2. Create a replicated region for an Azure Container Registry. (auto-generated) 

az acr replication create --location westus --registry myregistry --resource-group MyResourceGroup 

ACR will sync images across the selected regions. The process may take time based on image size. 

Considerations: 

• Each region operates independently after setup. 
• Azure Traffic Manager directs requests to the closest region. 
• Larger images take longer to replicate. 
• Configure regional webhooks to track push events. 
• For high availability, enable zone redundancy in each region. 

Deleting a Replica: 

• In Azure Portal, go to Replications, select the replica, and click Delete. 
• Or use the Azure CLI: 

az acr replication delete --name <region> --registry <registry-name> 

Pricing: 

• Geo-replication is available in the Premium tier. 
• Each replicated region incurs separate Premium fees. 
• Reduces network egress costs by keeping images local.  

Conclusion 

Choosing the right container registry depends on your organisation's cloud strategy and specific requirements. 

• Google Container Registry (GCR) is the best fit for organizations using Google Cloud services and requiring high availability with minimal configuration. 
• Amazon Elastic Container Registry (ECR) is ideal for enterprises leveraging AWS services, offering deep integration and robust security features. 
• Azure Container Registry (ACR) stands out for its geo-replication, task automation, and flexible pricing tiers, making it suitable for Azure-centric environments. 

By understanding the key features, advantages, and use cases of GCR, ECR, and ACR, you can make an informed decision that aligns with your cloud-native application needs. 

 Choosing the right container registry is key to smooth and efficient deployments. Whether you're using Google Cloud, AWS, or Azure, understanding the differences can help you make the best decision. Have questions or need help setting up your container registry? Reach out to us today and get started!