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.
Scenarios
- Scenarios where frequent interactions and adjustments are required in different runtime environments including development, test, and production environments, such as DevOps and microservice.
- Scenarios where multiple projects are incubated at the same time and applications are delivered or released on a frequent basis, such as container cloud-native and mobile game.
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 advanced payment. After you estimate the required storage capacity based on historical data and your budget, you can purchase SCUs and create pay-as-you-go disks to fulfill your storage requirements.
Comparison between different purchase methods of disks
| Purchase method | Purpose | Form | Scenario |
|---|---|---|---|
| SCU | Offsets the hourly bills of pay-as-you-go disks. | A subscription storage resource plan that requires an all-upfront payment. It is used to offset the bills of pay-as-you-go disks but does not provide storage capacity. | For more information, see the Scenarios section in this topic. |
| Pay-as-you-go disk | Can be resized, encrypted, attached to or detached from an ECS instance, and have snapshots. | A disk that provides storage capacity and uses the pay-as-you-go billing method. | Applications or services with burst traffic such as temporary scaling, temporary testing, and scientific computing. |
| Subscription disk | Can be resized, encrypted, attached to a subscription ECS instance, and have snapshots. | A disk that provides storage capacity and is purchased together with a subscription ECS instance. | Web services that have 24/7 support, or data disks that store data for subscription ECS instances for an extended period of time. |
Specifications
SCUs are measured by capacity. An SCU can have a capacity of 20 GiB, 40 GiB, 100 GiB, 500 GiB, 1 TiB, 2 TiB, 5 TiB, 10 TiB, 20 TiB, or 50 TiB. Different capacities are suited for different scenarios from daily use by developers to enterprise-level applications.
- Individual developers can purchase SCUs of 20 GiB to 500 GiB for daily use to have long-time cost-effectiveness and flexibility in the use of disks.
- SCUs of 1 TiB to 50 TiB are suitable for enterprise-level applications, which can meet the requirements that cloud-native scenarios (such as DevOps, microservice, and containerization) have for flexibility in the use of Elastic Block Storage (EBS) devices.
- SCUs can be used to offset the bills of enhanced SSDs (ESSDs), standard SSDs, ultra disks, and basic disks. SCUs cannot be used to offset the bills of local disks.
- SCUs can be used to offset the bills of Capacity Apsara File Storage NAS file systems and Performance NAS file systems. SCUs cannot be used to offset the bills of Extreme NAS file systems or Infrequent Access (IA) storage media.
- SCUs can be used to offset the bills of snapshots.
- SCUs can be used to offset the bills of Object Storage Service (OSS) Standard, Infrequent Access, and Archive storage classes.
Billing methods
SCUs use the subscription billing method. For more information, see Storage capacity units.
Limits
- 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 must fall within six months of the SCU creation.
- 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 management
- If you set Effective Time to Now when you purchase an SCU in the ECS console, the
following results occur:
The SCU takes effect at the top of the hour that you purchase the SCU and expires at 00:00:00 on the day following the expiration date. It can offset the bills of pay-as-you-go disks starting from the time it takes effect until it expires.
Assume that you purchase a 10 TiB SCU with a validity period of one year at 09:10:00 on August 20, 2019. The SCU takes effect starting 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 day following the expiration date. It can offset the bills of pay-as-you-go disks starting from the time it takes effect until it expires.
Assume that you purchase a 10 TiB SCU with a validity period of one year at 09:15:00 on August 20, 2019 and set the effective time of the SCU to 01:00:00 of 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.