Explanation
Why the waste happens and who it affects.
This often occurs after workloads are decommissioned but the file system is left behind. A quick indicator of this state is when the EFS file system has no mount targets configured. Without active usage or connection, these orphaned file systems represent pure cost with no functional value. Like EBS volumes, EFS file systems are billed for stored data whether or not anything is mounted, making it easy for unused resources to go unnoticed.
Billing model
The pricing dimensions that drive this cost.
EFS is billed based on:
- Total data stored (per GB/month)
- Storage class (Standard, Infrequent Access, or Archive, with data moved to IA or Archive by lifecycle policies)
- Throughput: Elastic throughput (the default mode) bills per GB of data transferred, while Provisioned throughput bills for throughput provisioned above the baseline included with Standard storage
Even when unmounted, EFS continues to accrue storage cost until deleted.
How to detect
5 checks to find it in your estate.
- Identify EFS file systems with no mount targets present
- Exclude file systems that are replication destinations (check DescribeReplicationConfigurations); Amazon EFS creates destination file systems without mount targets by design
- Check for file systems with no recent read/write activity over a representative time window
- Correlate with decommissioned EC2 instances or workloads that previously used the file system
- Confirm with workload owners whether the data is still required or can be deleted
How to fix
3 ways to remove the waste.
- Delete EFS file systems that are no longer in use and have no attached mount targets
- If data must be retained, consider exporting it to a lower-cost storage service (e.g., S3 Glacier) before deletion
- Establish periodic audits to identify and clean up orphaned file systems
Documentation
Vendor references for pricing and configuration.