Explanation
Managed Disks frequently remain detached after Azure virtual machines are deleted, reimaged, or reconfigured. Many persist unintentionally due to insufficient cleanup automation. Inactive detached disks generate unnecessary costs despite not supporting active workloads.
Relevant Billing Model
Managed Disks incur charges based on provisioned capacity (per GB/month) regardless of attachment status. Various disk types exist — Premium SSD, Standard SSD, Standard HDD, Ultra Disk — with separate IOPS/throughput billing. Snapshots are billed independently by storage consumed. Unattached disks remain fully billable until explicitly removed.
Detection
- Identify unattached Managed Disks not linked to any VM
- Review metrics and activity logs for read/write operations during evaluation period
- Verify intentional retention for recovery, migration, or reattachment purposes
- Determine if snapshots exist or are required before deletion
- Consult workload owners regarding business or technical necessity
Remediation
- Remove inactive detached Managed Disks no longer serving operational needs
- Create snapshots beforehand if data preservation is required
- Establish periodic reviews or implement automated cleanup processes to minimize persistent storage expenses, particularly for premium-tier disk types