Storage capacity units (SCUs) are subscription storage resource plans that can be used to offset the storage fees of various Alibaba Cloud storage services. Compared with storage plans that are dedicated to specific storage services, SCUs are more flexible and cost-effective.
Scenarios
SCUs are suitable for scenarios that require low storage costs and high flexibility in disk creation. Examples:
Scenarios in which frequent interactions and adjustments are required in different runtime environments, including development, testing, and production environments, such as DevOps and microservices.
Scenarios in which multiple projects are incubated at the same time and applications are delivered or released on a frequent basis, such as container cloud-native scenarios and mobile games.
You can use SCUs in one of the following patterns:
Pattern 1: You have created multiple pay-as-you-go disks. The historical bills of these disks show an approximate monthly average of disk space consumption. You can purchase SCUs to reduce monthly storage costs.
Pattern 2: The cost budget for a quarter or fiscal year has been planned in advance and requires a centralized purchase or advance payment. After you estimate the required storage capacity based on historical data and your budget, you can purchase SCUs and then create pay-as-you-go disks based on your storage requirements.
Billing method
SCUs support the subscription billing method. You are charged based on the capacity and validity periods of SCUs. For more information, see Storage capacity units.
Supported services
The following table describes the services to which SCUs can be applied.
Service | Offset rule |
Cloud disks | |
OSS | |
NAS | |
Snapshots |
Offset rules
After you purchase an SCU in a region, the SCU automatically matches eligible pay-as-you-go storage resources in that region to offset their bills until the SCU expires. When the deductible used capacity exceeds the SCU capacity, the excess capacity is billed on a pay-as-you-go basis. For more information, see Offset rules.
Limits
The following limits apply to SCUs:
SCUs can be used to offset the bills of only pay-as-you-go resources. SCUs cannot be used to offset the bills of pay-as-you-go disks attached to preemptible instances.
You can configure an effective time for each SCU. The configured time can be up to six months from the creation time of the SCU.
You cannot call API operations to create or manage SCUs.
The capacity limits of SCUs are determined by the capacity of EBS devices in your account. For more information about the capacity limits of SCUs that you can purchase in a region, see Limits.
Lifecycle rules
If you set Effective Time to Now when you purchase an SCU in the ECS console, the following results occur:
The SCU takes effect on the hour when you purchase the SCU and expires at 00:00:00 on the next day after the expiration date. It can offset the bills of pay-as-you-go storage resources from the effective time to the expiration time.
For example, you purchase a 10-TiB SCU with a validity period of 1 year at 09:10:00 on August 20, 2019. The SCU takes effect at 09:00:00 on August 20, 2019 and expires at 24:00:00 on August 21, 2020.
If you set Effective Time to Specify Effective Time when you purchase an SCU in the ECS console, the following results occur:
The SCU takes effect at the specified time and expires at 00:00:00 on the next day after the expiration date. It can offset the bills of pay-as-you-go storage resources from the effective time to the expiration time.
Assume that you purchase a 10-TiB SCU with a validity period of 1year at 09:15:00 on August 20, 2019 and set the effective time of the SCU to 01:00:00 on November 19, 2019. The SCU takes effect at 01:00:00 on November 19, 2019 and expires at 24:00:00 on November 20, 2020.
