Google Compute Engine – Remove Unattached Disks

Identify and remove unattached Google Compute Engine persistent disks to eliminate unnecessary cloud storage costs and optimize cloud resource management.

Why Unattached Disks Matter

Unattached disks are persistent storage volumes in Google Cloud that exist without being connected to any active compute instance. These orphaned disks typically accumulate through:

• Instance migration projects
• Diagnostic drive snapshots
• Abandoned backup volumes
• Incomplete instance deletion processes

When instances are deleted, Google Cloud does not automatically remove associated disks by default. This oversight can lead to continuous billing for unused storage resources.

Cost Implications and Savings Potential

Financial Impact

• Average Cost Savings: Organizations can typically reduce cloud storage expenses by 15-25% by removing unattached disks
• Hourly Billing: Unattached disks continue to incur charges even when not in use
• Potential Annual Savings: A medium-sized enterprise might save $5,000-$15,000 annually by implementing this policy

Savings Example

Consider a scenario with 50 unattached disks:

• Standard persistent disk: $0.04 per GB-month
• Average disk size: 500 GB
• Monthly unnecessary cost: $1,000
• Annual unnecessary cost: $12,000

Implementation Guide

Infrastructure-as-Code Remediation Example (Terraform)

resource "google_compute_disk" "example" {
  # Only create disks currently in use
  name = "attached-disk"
  type = "pd-standard"
  zone = "us-central1-a"

  # Add lifecycle rules to manage disk attachment
  lifecycle {
    prevent_destroy = false
  }
}

Manual Removal Steps

1. Navigate to Google Cloud Console
2. Open Compute Engine > Disks
3. Filter for unattached disks
4. Select unnecessary disks
5. Click “Delete” to remove

Best Practices

• Implement regular disk audits
• Create automated cleanup scripts
• Use cloud cost management tools like Infracost to proactively identify unattached resources
• Establish clear tagging and resource lifecycle policies

Recommended Tools

• Infracost: Provides automated scanning and cost optimization recommendations
• Google Cloud CLI: Supports bulk disk management
• Custom Scripts: Develop organization-specific cleanup automation

Real-World Scenarios

Scenario 1: Development Environment

A software development team migrates infrastructure between environments, leaving behind 30 unattached disks. By removing these, they save approximately $600 monthly.

Scenario 2: Research Project Cleanup

After completing a research project, computational resources were terminated but associated disks remained. Removing 15 unattached disks saved $300 per month.

Potential Considerations

Risks and Caveats

• Ensure no critical data exists on unattached disks before deletion
• Verify no pending restore or backup processes depend on these volumes
• Maintain comprehensive documentation of disk removal activities

When to Be Cautious

• During active migration processes
• When supporting long-term archival storage
• In environments with complex, interconnected systems

Frequently Asked Questions (FAQs)