# Amazon FSx File System

> Amazon FSx bills provisioned storage per GB-month and provisioned throughput per MBps-month, whether the file system is busy or empty. All 4 file system types (Windows, Lustre, ONTAP, OpenZFS) share that meter shape. ZopNight discovers file systems every 6 hours and recommends capacity rightsizing against actual usage.

Source: https://zop.dev/integrations/aws/fsx
Updated: 2026-08-19

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Amazon FSx provides managed Windows File Server, Lustre, NetApp ONTAP, and OpenZFS file systems billed on provisioned storage and throughput capacity. Provisioned capacity bills whether used or not, so oversized file systems carry a fixed monthly premium.

## Provisioned on two axes

FSx bills what you reserve, not what you use, on two independent axes: storage capacity per GB-month and throughput capacity per MBps-month, each chosen at creation. A file system provisioned at 2 TB and high throughput bills that configuration around the clock even if it holds 200 GB and serves a handful of clients. Backups add per GB-month on top, and rates differ across the four file system types, and SSD versus HDD storage classes in some of them widen the spread further.

## Sizing decisions that never got revisited

FSx file systems are sized at migration time, under uncertainty, with safety margin. Unlike EFS, which grows and shrinks by itself, the provisioned figure persists until someone changes it. Common shapes: the Windows file server provisioned at double the on-premises share it replaced, the Lustre scratch file system built for one heavy job and kept, and throughput capacity set high for a bulk load that finished months ago. Each is a fixed monthly premium for headroom that metrics show is never touched.

## The rightsizing loop

File systems are discovered on the 6-hour cycle, with per-resource cost from Cost Explorer or CUR 2.0 and capacity rightsizing recommendations that compare provisioned storage and throughput against actual consumption. There is no stop operation: an FSx file system bills its provisioned configuration until reconfigured or deleted, so the savings action is adjusting the provisioned numbers downward where supported, or migrating and retiring where not.

## Capacity figures in the console

FSx console, then File systems. Each row shows type, storage capacity, and throughput capacity; the detail page's usage graphs against those provisioned figures make the headroom, and the overpayment, visible in one view.