Storage capacity units (SCUs) are subscription storage resource plans that can be used to offset the pay-as-you-go bills of various storage resources. Compared with disks purchased together with subscription Elastic Compute Service (ECS) instances or resource plans of a specific resource, SCUs offer a better combination of cost-effectiveness and flexibility together with pay-as-you-go resources.
Offset rules
SCUs can be used to offset the storage fees of multiple Alibaba Cloud storage services. The following table describes the rules that apply when you use SCUs to offset the storage fees of the snapshot service in regions in the Chinese mainland.
| Type | Offset factor | Description |
|---|---|---|
| Regular snapshot | 0.08 | Each GiB of regular snapshot storage consumes 0.08 GiB of an SCU. |
Offset order
You are charged based on the size and storage duration of snapshots. By default, the pay-as-you-go billing method is used. You can use Object Storage Service (OSS) storage plans or SCUs to offset the bills of snapshots and reduce costs. You are charged for a snapshot from the point in time when it is created to the point in time when it is released.
The storage fees of snapshots are offset based on the following order: OSS storage plans > SCUs > pay-as-you-go bills.
Examples
Your stored snapshots are 500 GiB in size in January 2022. You have purchased an OSS storage plan of 200 GiB and an SCU of 40 GiB. The following table describes the storage fees calculated for the current month.
| Type | Offset by storage plan | Offset by SCU |
|---|---|---|
| Regular snapshot | An OSS storage plan of 200 GiB offsets the snapshot storage of 200 GiB. | The remaining 300 GiB of the snapshot storage is offset by 24 GiB of the SCU. 24 GiB specifies the SCU that is consumed by the remaining 300 GiB, except the snapshot storage of 200 GiB offset by the OSS storage plan. (500 GiB - 200 GiB) × 0.08 = 24 GiB |