Ensuring data durability and resilience is an essence of robust infrastructure design. While it's common to configure backups within a single region where the data resides, certain compliance or business requirements might demand multi-region backups. This blog explores how to achieve multi-region backups using Terraform by extending existing backup infrastructure.
Core Configuration: Primary Region Backup
To start, a Backup Vault is created to securely store backup data, encrypted with an AWS KMS key. A Backup Plan on the other hand specifies rules for scheduling, lifecycle management, and retention periods. These rules include the following:
- Backup Vault Reference: All backups are directed to the vault.
- Retention and Cold Storage: Policies like deleting backups after a certain number of days or transitioning to cold storage.
- Additionally, IAM roles are configured to allow the AWS Backup service to access the necessary resources.
Example Terraform configuration:
resource "aws_backup_vault" "example" {
name = "example_backup_vault"
kms_key_arn = aws_kms_key.example.arn
}
resource "aws_backup_plan" "example" {
name = "tf_example_backup_plan"
rule {
rule_name = "tf_example_backup_rule"
target_vault_name = aws_backup_vault.example.name
schedule = "cron(0 12 * * ? *)"
lifecycle {
delete_after = 14
}
}
advanced_backup_setting {
backup_options = {
WindowsVSS = "enabled"
}
resource_type = "EC2"
}
}
With this configuration, backups are securely stored in the region of deployment. However, to enhance resilience, we can extend this setup to support cross-region backups.
Extending to Cross-Region Backups
To enable cross-region backups, you’ll need:
- Secondary Provider Configuration: Define a provider for the secondary region to handle the resources there.
- Cross-Region Vault: Create a new backup vault in the secondary region with its KMS key for encryption.
- Backup Plan Copy Action: Modify the backup plan in the primary region to include a copy action. This ensures backups are automatically replicated to the secondary region, with their own lifecycle policies for retention and cold storage.
Step 1: Define a new AWS Provider
Add a new provider block for the target region:
provider "aws" {
alias = "backup"
region = "eu-west-1" # Specify the secondary region
}
Step 2: Create a Cross-Region Backup Vault
Provision a backup vault in the secondary region:
resource "aws_backup_vault" "backup" {
provider = aws.backup
name = var.vault_name
kms_key_arn = data.aws_kms_key.backup.arn
}
Step 3: Access the KMS Key
Since the vault requires encryption, retrieve or create a KMS key in the secondary region:
data "aws_kms_key" "backup" {
provider = aws.backup
key_id = var.kms_key_arn_backup
}
Step 4: Forward Variables Through Modules
If your Terraform project uses modules, ensure variables like kms_key_arn and vault_name are passed to the respective child modules for multi-region configuration.
Challenges and Best Practices
- Synchronization: Keep the backup schedules consistent across regions.
- Access Control: Ensure IAM roles have the appropriate cross-region permissions.
- Cost Considerations: Multi-region backups may incur additional costs for storage and data transfer.
- Module Design: Modularize the code to avoid duplication when configuring resources for multiple regions.
Benefits of Multi-Region Backups
- Increased Resilience: Protect against regional outages.
- Compliance: Meet data governance and disaster recovery standards.
- Business Continuity: Minimize downtime during regional failures.
Conclusion
By leveraging Terraform, you can easily extend your existing backup configuration to support multi-region setups. With proper planning and modularized code, adding a secondary backup region ensures enhanced data protection without significantly increasing complexity.
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