This topic describes the billable items, billing cycle, and billing methods of a General-purpose NAS file system.This topic also provides several billing examples.

Billable items

Billable item Description
Storage usage The maximum used storage space of the file system. Fees are calculated based on the maximum used storage space per hour.
  • The used storage space indicates the total size of all files in a file system. The size of directories is not counted. The basic storage unit is 4 KiB. If the size of a file is less than 4 KiB, the billed storage space of the file is rounded up to 4 KiB. If the size of a file is larger than 4 KiB, the billed storage space is rounded up to the nearest multiple of 4 KiB. For example, if the size of a file is 2 KiB, the size of the file is counted as 4 KiB. If the size of a file is 6KiB, the size of the file is counted as 8 KiB.
  • File holes occupy storage space in NAS. Therefore, you are billed for the file holes in your NAS file system. A file hole consists of zeros that are not written to a file. A file hole can be created by using the truncate, lseek, or fallocate command.

Billing cycle

The fees incurred within an hour are deducted from your account balance in the next hour. For example, you are billed at 09:30 for the fees incurred from 08:00 to 09:00.

Note If you receive a bill at 09:30, the bill may include fees only from 07:00 to 08:00 due to system latency.

Billing methods

If your Alibaba Cloud account uses storage plans and storage capacity units (SCUs) at the same time, storage plans are deducted first. If your storage plans have an insufficient balance, SCUs are deducted. If your storage plans and SCUs are both exhausted, the billing method is changed to pay-as-you-go.

  • Storage plan

    You can purchase a storage plan to deduct the resource usage fees of a General-purpose NAS file system. You can reserve resources and reduce costs by using storage plans.

    • Purchase method

      For more information about how to purchase storage plans, see Purchase a storage plan.

    • Usage rules
      • After you purchase a storage plan, NAS deducts fees from the storage plan based on the used storage space of your file system.
      • A General-purpose NAS file system can be attached to only one storage plan at a time. If you delete a General-purpose NAS file system, its storage plan is automatically detached. You can attach the storage plan to another General-purpose NAS file system. However, the new file system must be of the same type and reside in the same region as the file system that you want to delete.
    • Renewal and upgrade

      You can renew and upgrade a storage plan. For more information, see Manage storage plans.

Examples

Example 1: Mr. Wang has created a Capacity NAS file system in the China (Hangzhou) region. The average space usage per hour in January of 2021 is 1 TiB. The following table lists the monthly fees that were incurred by the file system based on storage plans and the pay-as-you-go billing method.
Billing method Fee
Pay-as-you-go Space usage fee = 1,024 GiB × 0.06 USD/GiB/month = USD 61.44
Storage plan (500 GiB, one month) Space usage fee = USD 23 + (1024 GiB - 500 GiB) × 0.06 USD/GiB/month = USD 54.44

In the preceding equation, USD 23 is the fee for the storage plan (500 GiB, one month).
Storage plan (1 TiB, one month) Space usage fee = USD 48

In the preceding equation, USD 48 is the fee for the storage plan (1 TiB, one month).
Example 2: Mr. Zhang has created a Performance NAS file system in the China (Hangzhou) region. The average space usage per hour in January of 2021 is 1 TiB. The following table lists the monthly fees that were incurred by the file system based on storage plans and the pay-as-you-go billing method.
Billing method Fee
Pay-as-you-go Space usage fee = 1,024 GiB × 0.3 USD/GiB/month = USD 307.2
Storage plan (500 GiB, one month) The 500 GiB is deducted by the storage plan, and the fee for the remaining space usage is calculated based on the pay-as-you-go billing method.

Space usage fee = USD 133 + (1024 GiB - 500 GiB) × 0.3 USD/GiB/month = USD 290.2

In the preceding equation, USD 133 is the fee for the storage plan (500 GiB, one month).
Storage plan (1 TiB, one month) Space usage fee = USD 272

In the preceding equation, USD 272 is the fee for the storage plan (1 TiB, one month).

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