Block storage devices - Elastic Compute Service - Alibaba Cloud Documentation Center

This topic describes the billing of block storage devices, including the purchase, pricing, billing rules, and billing examples of local disks and Elastic Block Storage (EBS) devices such as cloud disks. This topic also describes changes in billing when disk specifications are changed.

Purchase and pricing

Block storage devices are classified into cloud disks, such as Enterprise SSDs (ESSDs) and standard SSDs, and local disks. Local disks are available only for specific instance types and cannot be separately purchased. The local disk fees are included in the instance type fees. For information about local disks, see Local disks. The following section describes the purchase and pricing of cloud disks.

Purchase: Go to the Disk page.
Pricing: The prices of cloud disks vary based on the region. For more information, go to the Pricing tab of the Elastic Compute Service (ECS) product page.

Billing of cloud disks

Billing rules

Billable item	Category	Billing rule	Billing method
Disk capacity	All cloud disks	Billing starts at the point in time when a cloud disk is created, regardless of whether the disk is attached to ECS instances.	Subscription: Cloud disk capacity (GiB) × Unit price × Subscription duration. Note If the actual usage time is less than the purchased time, you can apply for a refund for the cloud disk. For more information, see Refunds. Pay-as-you-go: Cloud disk capacity (GiB) × Unit price × Usage duration. Storage capacity units (SCUs): a subscription-based storage resource plan that can be used to offset pay-as-you-go bills based on offset factors. If the amount of used storage exceeds the capacity of an SCU, you are charged for the excess storage usage at the pay-as-you-go rates.
Provisioned performance	ESSD AutoPL disks	You are charged for the performance provision fees of ESSD AutoPL disks for which the performance provision feature is enabled and the provisioned IOPS is configured. Bills are generated on an hourly basis.	Pay-as-you-go: Unit price of provisioned performance × Provisioned IOPS × Usage duration.
Burst performance	ESSD AutoPL disks	By default, the performance burst feature is enabled for ESSD AutoPL disks. Burst performance is defined as the portion of performance (IOPS or throughput, whichever is higher) that exceeds the sum of the baseline performance and provisioned performance of the disk. Burst performance is billed in 1-second increments, and bills for burst performance are generated on an hourly basis. Burst performance is calculated in terms of burst I/O operations in 1-second increments based on the following rules: Note The unit price of burst performance is calculated per 10,000 I/O operations. For billing purposes, burst I/O operations are rounded up to the next 10,000 operations. Burst performance = Total performance - (Baseline performance + Provisioned performance). If only burst IOPS is generated, the number of burst I/O operations is calculated based on the following formula: Burst I/O operations = ∑_{(Burst IOPS × Duration in seconds)}. For example, if an ESSD AutoPL disk bursts to 10,000 IOPS for 2 seconds and then bursts to 8,000 IOPS for 3 seconds, the number of burst I/O operations is calculated based on the following formula: Burst I/O operations = 10,000 IOPS × 2 + 8,000 IOPS × 3 = 44,000. Then, the value is rounded up to 50,000. If only burst throughput is generated, the number of burst I/O operations is calculated based on the following formula: Burst I/O operations = ∑_{(Burst throughput/16 KB × Duration in seconds)}. For example, if an ESSD AutoPL disk bursts to a throughput of 1 GB/s (1 × 1,024 × 1,024 = 1,048,576 KB/s) for 2 seconds, the number of burst I/O operations is calculated based on the following formula: Burst I/O operations = 1,048,576/16 × 2 = 131,072. Then, the value is rounded up to 140,000. If burst IOPS and burst throughput are both generated, the number of burst I/O operations is calculated based on the following formula: Burst I/O operations = max{I/O operations of burst IOPS, I/O operations of burst throughput}. For example, if an ESSD AutoPL disk bursts to 8,000 IOPS and a throughput of 1 GB/s for 2 seconds, the number of burst I/O operations that is calculated by using the burst IOPS (8,000 × 2 = 16,000) is rounded up to 20,000, and the number of bust I/O operations that is calculated by using the burst throughput (1,048,576/16 × 2 = 131,072) is rounded up to 140,000. You are charged for 140,000 burst I/O operations.	Pay-as-you-go: Unit price of burst performance × Burst I/O operations/10,000.

Billing methods

The billing methods of cloud disks vary based on how the disks are created.

Created together with ECS instances: use the same billing method as the instances.
Separately created and then attached to ECS instances:
- If the disks are attached to subscription instances, the disks support the subscription and pay-as-you-go billing methods.
- If the disks are attached to pay-as-you-go instances, the disks support only the pay-as-you-go billing method.
Separately created and not attached to ECS instances: support only the pay-as-you-go billing method.

Change the billing method of a cloud disk

You can change the billing method for specific types of cloud disks. For more information, see Change the billing method of a disk.

Billing for changed disk specifications

The billing of your cloud disk may change when you perform the operations described in the following table.

Operation	Billing	References
Resize a cloud disk	When you extend the disk capacity to resize a cloud disk, you are charged for the additional capacity. Note When you resize a cloud disk, you cannot change the billing method of the disk.	Overview
Change the category of a cloud disk	After you change the category of a cloud disk, you are charged for the disk based on the new category.	Change the category of a disk
Change the performance level of an ESSD	After you change the performance level of an ESSD, you are charged for the ESSD based on the new performance level.	Change the performance level of an ESSD.
Modify the performance configurations of an ESSD AutoPL disk	If you enable the performance provision and performance burst features for an ESSD AutoPL disk or if you modify the provisioned IOPS of an ESSD AutoPL disk, you are charged for the ESSD AutoPL disk based on the new performance configurations.	Modify the performance configurations of an ESSD AutoPL disk

Billing of local disks

Local disks are available only to specific instance types and cannot be separately purchased. The prices of local disks are included in the prices of instance types. For more information, see Local disks.

For information about instance families that are equipped with local disks, see Overview of instance families.

Billing examples

For example, you purchase a system disk and a data disk when you create an instance in the China (Hangzhou) region.

System disk: a PL0 ESSD with a capacity of 50 GiB
Data disk: a PL1 ESSD with a capacity of 100 GiB

The following table describes how the disks are billed.

Note

The prices in the following table are provided only for reference. The prices displayed on the Pricing tab of the ECS product page prevail.

Billing method	Billing condition	Fee (USD)
Subscription	System disk: The unit price of the PL0 ESSD is USD 7.65 per 100 GiB-month. Data disk: The unit price of the PL1 ESSD is USD 15.30 per 100 GiB-month. Subscription duration: one month	Fee for the system disk: Unit price of the system disk × Disk capacity × Subscription duration = 7.65 × (50/100) × 1 = 3.825. Fee for the data disk: Unit price of the data disk × Disk capacity × Subscription duration = 15.30 × (100/100) × 1 = 15.30. Total: 3.825 + 15.30 = 19.125.
Pay-as-you-go	System disk: The unit price of the PL0 ESSD is USD 0.0160 per 100 GiB-hour. Data disk: The unit price of the PL1 ESSD is USD 0.0320 per 100 GiB-hour. Usage duration: 24 hours.	Fee for the system disk: Unit price of the system disk × Disk capacity × Usage duration = 0.0160 × (50/100) × 24 = 0.192. Fee for the data disk: Unit price of the data disk × Disk capacity × Usage duration = 0.0320 × (100/100) × 24 = 0.768. Total: 0.192 + 0.768 = 0.96.