A Storage Capacity Unit (SCU) is a prepaid resource plan for cloud storage capacity. It offsets storage fees for multiple cloud storage products, such as disks, snapshots, and Object Storage Service (OSS). This topic describes the billing method, offset rules, and refund policy for SCUs.
Billing method
SCUs use a subscription billing method based on capacity and validity period. Payment is all upfront, meaning you must pay the full amount at purchase. The fee is calculated as follows:
Upfront fee = SCU unit price × validity period
SCU unit price: For detailed pricing, see Pricing.
Validity period: Choose from 1 month, 2 months, 3 months, 6 months, 1 year, 3 years, or 5 years. Annual payments offer a discount.
For example, if you purchase a 100 GB Storage Capacity Unit (SCU) for 2 months in the China (Beijing) region, and the unit price for the SCU is 100 CNY/month, the total upfront fee is: Upfront fee = 100 CNY/month * 2 months = 200 CNY.
Purchase and use SCU
To purchase an SCU, see Purchase a Storage Capacity Unit (SCU).
After purchasing an SCU, it automatically offsets pay-as-you-go bills for disks and snapshots in the same region. If your actual disk and snapshot usage exceeds the SCU capacity, the excess is billed on a pay-as-you-go basis.
Offset rules
Offset factor
The following table lists offset factors for disks and snapshots in the China (Beijing) region. For offset factors in other regions or for other cloud products, see Pricing.
Type | Offset factor | Description |
Ultra Disk | 0.35 | Each 0.35 GB of SCU capacity offsets 1 GiB of ultra disk. |
Standard SSD | 1 | Each 1 GB of SCU capacity offsets 1 GiB of standard SSD. |
PL0 ESSD | 0.5 | Each 0.5 GB of SCU capacity offsets 1 GiB of PL0 ESSD. |
PL1 ESSD | 1 | Each 1 GB of SCU capacity offsets 1 GiB of PL1 ESSD. |
PL2 ESSD | 2 | Each 2 GB of SCU capacity offsets 1 GiB of PL2 ESSD. |
PL3 ESSD | 4 | Each 4 GB of SCU capacity offsets 1 GiB of PL3 ESSD. |
Standard snapshot | 0.12 | Each 0.12 GB of SCU capacity offsets 1 GB of standard snapshot. |
Offset order
cloud disk
SCUs offset only pay-as-you-go disk storage fees to reduce costs. The offset order is: SCU > pay-as-you-go. For more disk billing details, see Block Storage billing.
Snapshots
Snapshots support offsetting pay-as-you-go storage fees using OSS Standard - locally redundant storage plans, SCUs, or reserved capacity to reduce costs.
If you have purchased reserved capacity in a region, you cannot purchase an OSS Standard - locally redundant storage plan in the same region. Therefore, the offset order for snapshot storage fees falls into two scenarios:
OSS Standard - locally redundant storage plan > SCU > pay-as-you-go
Reserved capacity > SCU > pay-as-you-go
For more snapshot billing details, see Snapshot billing.
Offset examples
Using SCUs to offset disk storage fees
Example 1: You use a PL1 ESSD with a total capacity of 10 TiB and purchase a 10 TB SCU.
The SCU capacity consumed is 10 TB (10 TB × 1). Your 10 TB SCU fully offsets the pay-as-you-go bill for this disk.
Example 2: You use a PL0 ESSD with 10 TiB and a PL1 ESSD with 5 TiB, and purchase a 10 TB SCU.
The SCU capacity consumed is 10 TB (10 TB × 0.5 + 5 TB × 1). Your 10 TB SCU fully offsets the pay-as-you-go bills for these disks.
Example 3: You use a PL3 ESSD with 1 TiB, a PL2 ESSD with 2 TiB, and a PL1 ESSD with 2 TiB, and purchase a 10 TB SCU.
The SCU capacity consumed is 10 TB (1 TB × 4 + 2 TB × 2 + 2 TB × 1). Your 10 TB SCU fully offsets the pay-as-you-go bills for these disks.
Example 4: You use a standard SSD with 12 TiB and purchase a 10 TB SCU.
The SCU capacity consumed is 12 TB (12 TB × 1). Following the offset order (SCU > pay-as-you-go), your 10 TB SCU offsets 10 TiB of the pay-as-you-go bill, and the remaining 2 TiB is billed on a pay-as-you-go basis.
Using SCUs to offset snapshot storage fees
Example 1: In January 2022, your snapshot size in the China (Beijing) region is 500 GB. How much OSS Standard - locally redundant storage plan and SCU must you purchase to fully offset the snapshot storage fees?
OSS Standard - locally redundant storage plan: Purchase 500 GB to fully offset.
SCU: Purchase 60 GB (500 × 0.12) to fully offset.
Example 2: In January 2022, your snapshot size in the China (Beijing) region is 500 GB. You purchase a 200 GB OSS Standard - locally redundant storage plan and a 40 GB SCU. How does the SCU offset the snapshot storage fees?
Following the offset order (OSS Standard - locally redundant storage plan > SCU > pay-as-you-go), the offset process is as follows:
First, use the OSS Standard - locally redundant storage plan to offset snapshot storage fees.
The 200 GB OSS Standard - locally redundant storage offsets 200 GB of snapshot storage fees.
Then, use the SCU to offset snapshot storage fees.
The remaining 300 GB of snapshots requires (500 GB – 200 GB) × 0.12 = 36 GB of SCU capacity. Use 36 GB of SCU to offset the remaining 300 GB of snapshot storage fees.
Expiration
After an SCU expires, it can no longer offset pay-as-you-go bills for storage products. If no other SCUs exist in the region, all previously offset storage products revert to pay-as-you-go billing.
Renewal or upgrade
SCUs do not support renewal or upgrade. However, you can purchase additional SCUs as needed based on your storage usage.
If your current SCU capacity is insufficient, purchase multiple SCUs to stack their capacities.
If your SCU is about to expire, repurchase an SCU before expiration and specify its effective time.
Refund
You can request a no-questions-asked refund within five days of purchasing an SCU.
Each Alibaba Cloud account is eligible for one no-questions-asked SCU refund per year. The maximum refundable amount is one SCU.
Refunds deduct any consumed amount. Discounts from coupons or promotions are not refunded. For more information, see Refund policy and process.
References
Call the PurchaseStorageCapacityUnit API to purchase one or more SCUs.
Call the ModifyStorageCapacityUnitAttribute API to modify the name or description of an SCU.
Call the DescribeStorageCapacityUnits API to query SCU details, such as capacity and status.
FAQ
For common questions about SCUs, see Billing FAQ.