Basic Concept

The usage and access frequency of different types of data are different. Also, there is an aging curve for the data. With the gradual aging of the data, the access frequency gradually decreases, and the data enters the archiving status. The hierarchical storage is a methodology, that is, different types of data are stored in different storage types to reduce the total storage cost and meet the service requirements.

Storage Types

BOS provides four storage types for different storage scenarios, i.e., standard storage, infrequent access, cold storage, and archive storage. You can specify the storage type of the objects during file upload. In this case, the storage type of objects specified during file upload should prevail. Furthermore, you can also set the default storage type of buckets. If the storage type is not specified during file upload, the file inherits the default storage type of buckets.

Description: For the pricing information of various storage types, please see the [Storage Cost](https://cloud.baidu.com/doc/BOS/s/Ok1rmtaow#Storage Cost#). For specific billing mode, see Billing Items.

Standard Storage-Multi-AZ

• The standard storage - multi-AZ provides users with high-reliability, -available, and -performance object storage service.
• A piece of data is synchronously stored in three availability zones, achieving high reliability and having cross-data center disaster recovery capability.
• The standard storage - multi-AZ is applicable for scenarios requiring frequent data reading and high reliability.

Standard storage

• The standard storage provides users with high-reliability, -available, and -performance object storage service.
• The standard storage is applicable for scenarios requiring frequent data reading.

Infrequent Access-Multi-AZ

• The infrequent access - multi-AZ provides users with reliable and lower-cost object storage service.
• A piece of data is synchronously stored in three availability zones, achieving high reliability and having cross-data center disaster recovery capability.
• The infrequent access is applicable for the data requiring long-term storage and less access.
• The infrequent access is consistent with the standard storage in terms of online access performance, persistence and availability, but its price is much lower than that of the standard storage.

Infrequent access

• Infrequent Access provides users object storage services with high reliability and low storage cost;
• The infrequent access is applicable for the data requiring long-term storage and less access.
• The infrequent access is consistent with the standard storage in terms of online access performance, persistence and availability, but its price is much lower than that of the standard storage.

Cold storage

• The cold storage provides users with reliable and low-cost object storage services.
• The cold storage is applicable for the data requiring long-term storage and less access.
• The cold storage is consistent with the standard storage and infrequent access in terms of online access performance, persistence, and availability, but its price is much lower than that of the standard storage and infrequent access.

Archive storage

• The archive storage provides users with reliable and extreme-low-cost object storage service.
• The archive storage is applicable for the data requiring long-term storage and rare access.
• The archive storage is consistent with the standard storage, infrequent access, and cold storage in terms of persistence and availability, but its price is much lower than that of the standard storage, infrequent access, and cold storage.

Comparison of Storage Types

Comparative Metrics	Standard Storage -Multi-AZ	Standard Storage	Infrequent Access with Multi-AZs	Infrequent Access	Cold Storage	Archive Storage
Availability	99.99%	99.95%	99.99%	99.95%	99.95%	99%
Minimum storage time	None	None	30 days	30 days	60 days	180 days
Data restoration cost	None	None	Bill-by-traffic (GB)	Bill-by-traffic (GB)	Bill-by-traffic (GB)	Bill-by-traffic (GB)
Data access characteristics	Real-time access, millisecond delay.	Real-time access, millisecond delay.	Real-time access, millisecond delay.	Real-time access, millisecond delay.	Real-time access, millisecond delay.	The data needs to be restored before reading. You need several hours to restore the data.
Applicable scenarios	Scenarios requiring extremely high reliability, such as mobile application, website video and data analysis.	Mobile application, website video, data analysis, etc.	Scenarios requiring extremely high reliability, such as online disk storage, monitoring data and media resource backup.	Online disk storage, monitoring data, media resource backup, etc..	Medical imaging, business backup and log data	Business scenario requiring long term data storage, such as gene data and compliance archive file.
Scenario characteristics	Frequent data reading scenarios.	Frequent data reading scenarios.	Scenarios where the average of monthly visits are less than 1.	Scenarios where the average of monthly visits are less than 1.	Scenarios with the average of annual accesses less than 1.	Scenarios with the average of three-year accesses less than 1.

Description:

• The data reliability is 99.9999999999% for the standard storage, standard storage - multi-AZ, infrequent access, infrequent access - multi-AZ, and cold storage, and 99.999999% for the archive storage.

Region Opening

The opening degree of each storage type for BOS varies in different regions. During the purchase, refer to the table below.

Region	Standard Storage -Multi-AZ	Standard Storage	Low frequency Storage-Mult-AZ	Infrequent Access	Cold Storage	Archive Storage
East China-Beijing	?	?	?	?	?	?
North China - Baoding	None	?	None	?	?	?
East China - Shanghai	?	None	None	None	None	None
East China-Suzhou	None	?	None	?	?	?
South China - Guangzhou	?	?	?	?	?	?
Central China China Finance - Wuhan	None	?	None	?	?	None
Hong Kong, China	None	?	None	?	None	None
Singapore	None	?	None	?	?	None

Considerations

• The archive storage is applicable for scenarios with an average of three-year accesses less than 1, e,g., gene data, compliance archive file, and archive medical data. The archive storage is not applicable for files requiring frequent access, or other storage types are selected, e.g., infrequent access (applicable for scenarios with the average of monthly accesses less than 1) and cold storage (applicable for scenarios with an average of annual accesses less than 1).
• The minimum storage period of the archive storage file is 180 days. If the storage period of the archive storage file is less than 180 days, for example, it is deleted when the storage period is less than 180 days, BOS charges for a minimum storage period of the archive storage and for the remaining time at one time?. BOS counts the remaining time accurate to the seconds and does not charge any additional cost from you.
• There is also a minimum storage period limit for infrequent access files and cold storage files. The minimum storage period of infrequent access files is 30 days, and the minimum storage period of cold storage files is 60 days. If there is the remaining storage time, a fee incurs for the minimum storage period, which is also charged according to the remaining time at one time.
• You need to restore the files before you read the infrequent access files, cold storage files, and archive storage files. You do not need to restore the standard storage files. When you access the infrequent access files and cold storage files, BOS automatically triggers the restoration operation for you according to the file storage type. Thus, it is not necessary for users to restore the files manually. When you want to access the archive storage files, you need to manually call the RestoreObject API to restore the files, or click "Restore File" on the File Information page of the console. The data restoration is a paid service, which is equivalent to BOS unfreezing the frozen files for you first, and the files can be normally accessed and read after unfreezing.
• The restoration speed of archive files is low, which is calculated in terms of hours. Therefore, the archive storage of BOS is not applicable for online business scenarios, e.g., real-time search and read, and BOS allows each user to restore up to 35 files per PB of archive storage files every day. After it is up to 35 files, the remaining files cannot be restored on the same day. Therefore, BOS recommends that you store the large files that are not used for a long time as the archive file. However, it does not recommend that you store the small files that need to be restored frequently as the archive storage.
• If the archived storage file is less than 64 KB, it is charged according to 64 KB. If the file is greater than or equal to 64 KB, it is charged according to the actual size.

Billing Mode

For the storage price, traffic fee, request fee, and data processing fee of each storage type, see Overview of Billing Items to learn more about billing items. For the price of billing items, see On-Demand Billing. You can also purchase the Resource Package in advance. The corresponding fee is automatically deducted from the resource package after the purchase.