Explanation
Why the waste happens and who it affects.
These overprovisioned settings can silently accrue substantial monthly charges that go unnoticed without intentional review.
This inefficiency is not flagged by AWS Trusted Advisor and is easy to miss. Elastic Throughput mode now offers a scalable alternative that automatically adjusts capacity - but isn't always cheaper, depending on the workload's sustained throughput.
Billing model
The pricing dimensions that drive this cost.
Amazon EFS supports three throughput modes (Elastic is the default and recommended mode):
Bursting Throughput Mode - Throughput scales with the amount of data in Standard storage (a baseline of 50 KiBps per GiB); short bursts above the baseline are supported using a credit system. No separate throughput charge.
Provisioned Throughput Mode - Throughput is explicitly configured in MB/s and billed for the throughput provisioned above the baseline included with Standard storage, regardless of actual usage.
Elastic Throughput Mode - Throughput scales automatically to meet demand and is billed for the amount of data and metadata read or written, with no included baseline and no provisioned charge.
Provisioned throughput is billed continuously, even if the application's actual throughput is far below the configured amount. Elastic mode eliminates this fixed cost but can be more expensive for sustained high throughput. AWS recommends Elastic when average throughput is 5% or less of peak, and Provisioned when it is 5% or more.
How to detect
6 checks to find it in your estate.
- Identify EFS file systems configured with Provisioned Throughput Mode
- Compare provisioned throughput (MB/s) to actual usage over time
- Assess whether throughput usage consistently falls below provisioned baseline
- Flag file systems in dev/test environments that mirror production settings
- Evaluate whether switching to Elastic Throughput/Bursting Throughput would reduce cost without affecting performance
- Confirm whether burst patterns might result in higher costs under Elastic mode
How to fix
4 ways to remove the waste.
- Reconfigure overprovisioned file systems with a reduced Provisioned Throughput value, noting that after switching to Provisioned mode or changing the provisioned amount, further decreases and switches to Elastic or Bursting are blocked for 24 hours
- For workloads with low and predictable throughput, consider switching to Elastic Throughput
- For dev/test systems cloned from production, adjust throughput settings independently
- Establish a periodic review of throughput configurations as part of FinOps or infrastructure governance
Documentation
Vendor references for pricing and configuration.