Azure Storage Blob Access Tiers

Azure Blob Storage offers different access tiers that can be used to store infrequently accessed data at the lowest cost, or hot data that is accessed frequently. By choosing the right access tier, you can optimize your storage costs.

The primary access tiers for Blob Storage are:

Hot tier: Optimized for storing data that is accessed or modified frequently. The Hot tier offers the highest storage cost, but the lowest access cost.
Cool tier: Optimized for data that is accessed infrequently or needs to be stored for at least 30 days. The Cool tier offers lower storage costs than the Hot tier, but higher access costs.
Archive tier: Optimized for data that is rarely accessed and stored for at least 180 days with flexible latency requirements. The Archive tier offers the lowest storage cost, but the highest access cost and retrieval times.

Understanding Access Tier Characteristics

Feature	Hot Tier	Cool Tier	Archive Tier
Frequency of Access	High	Infrequent	Rare
Storage Cost	Highest	Moderate	Lowest
Access Cost	Lowest	Moderate	Highest
Minimum Data Retention	None	30 days	180 days
Data Retrieval Time	Millisecond	Millisecond	Hours (typically 1-12 hours)

When to Use Each Tier

Tip: Carefully consider your data access patterns and retention policies to select the most cost-effective tier.

Hot Tier Use Cases

Data that is actively being developed or processed.
Frequently accessed website content or application data.
Content that needs to be readily available for users.

Cool Tier Use Cases

Long-term storage of data that is not accessed regularly but needs to be available for occasional retrieval.
Backup and disaster recovery data that is not frequently restored.
Older versions of files or documents.

Archive Tier Use Cases

Data that must be retained for regulatory compliance, but is accessed very rarely.
Archived media files or historical data that might be needed for legal discovery.
Cold data for long-term archival purposes.

Note: Rehydrating data from the Archive tier can take several hours. Ensure this latency is acceptable for your use case before moving data to Archive.

Setting Access Tiers

You can set the access tier for a blob or a container. When you set the tier for a container, all new blobs uploaded to that container will inherit the container's tier unless explicitly specified otherwise. Existing blobs in the container are not affected.

Setting Tier for a Blob

You can set the tier of an individual blob during upload or by modifying an existing blob. This is typically done using the Azure portal, Azure CLI, PowerShell, or SDKs.

Example using Azure CLI:


az storage blob set-tier --account-name <storage-account-name> --container-name <container-name> --name <blob-name> --tier Cool

Setting Tier for a Container

Setting a default tier for a container can simplify management for blobs that share similar access patterns.

Example using Azure CLI:


az storage container update --account-name <storage-account-name> --name <container-name> --default-blob-tier Hot

Warning: Deleting data from the Cool tier before the 30-day minimum retention period incurs a charge equivalent to the remaining retention period. Similarly, deleting data from the Archive tier before 180 days incurs charges for the remaining retention period.

Lifecycle Management

Azure Blob Storage offers lifecycle management policies that allow you to automatically transition blobs between access tiers based on rules you define. This helps in optimizing costs by moving infrequently accessed data to cooler tiers.

Lifecycle management policies can be configured to:

Transition blobs to a cooler tier (e.g., Hot to Cool, or Cool to Archive) based on age.
Delete blobs that are no longer needed after a certain period.

Conclusion

Choosing the appropriate access tier for your data in Azure Blob Storage is a crucial step in managing costs and ensuring performance. By understanding the characteristics and cost implications of the Hot, Cool, and Archive tiers, you can effectively optimize your storage solution.