Azure NetApp Files bills based on provisioned capacity pool size — not on the actual data stored within volumes. This means that when a capacity pool is provisioned at a size significantly larger than the sum of volume quotas allocated within it, the organization pays for stranded, unallocated capacity every hour. For example, a 10 TiB capacity pool with only 6 TiB of volume quotas allocated has 4 TiB of capacity that generates cost but serves no purpose.

This overprovisioning commonly occurs for several reasons. Capacity pools do not automatically shrink — since April 2021, pool sizing is entirely a manual customer responsibility. When volumes are deleted, the freed capacity remains in the pool unless an administrator explicitly resizes it downward. Additionally, with auto QoS pools, volume quotas directly determine throughput performance, which incentivizes teams to set larger quotas than their data requires, further inflating pool sizes. Over time, these dynamics create a growing gap between provisioned pool capacity and what is actually needed, resulting in persistent, avoidable charges that compound across multiple pools and regions.