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Storage Capacity Unit:Overview of SCUs

Last Updated:Jan 19, 2024

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 applicable to scenarios that require low storage costs and high flexibility in disk creation. Examples:

  • Scenarios where frequent interactions and adjustments are required in different runtime environments including development, testing, and production environments, such as DevOps and microservices.

  • 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 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 methods

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

Type

Offset rule

Cloud disks

  • Enhanced SSDs (ESSDs)

  • Standard SSDs

  • Ultra disks

  • Basic disks

Note

SCUs cannot be used to offset the storage costs of local disks.

Offset rules for EBS

OSS

  • Object Storage Service (OSS) Standard objects

  • OSS Infrequent Access (IA) objects

  • OSS Archive objects

Offset rules for OSS

NAS

  • Capacity NAS file systems

  • Performance NAS file systems

Note

SCUs cannot be used to offset the storage fees of Extreme NAS file systems or IA Storage Media.

Offset rules for NAS

Snapshots

Normal snapshots

Offset rules for the snapshot service

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 day following the expiration date. It can offset the bills of pay-as-you-go storage resources 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 at 09:00:00 on August 20, 2019 and expires at 24:00:00 on August 21, 2020.SCU生效失效示例图

  • 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 storage resources 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.SCU生效失效示例图-指定了生效日期

References