Blob Access Tiers
Azure Blob Storage offers different access tiers to optimize costs by storing blob data at the most appropriate price point. The access tiers are designed for different patterns of data access and retrieval. Choosing the correct tier can significantly impact your storage costs.
Understanding Access Tiers
Blob access tiers allow you to store infrequently accessed data in a low-cost tier and frequently accessed data in a high-performance tier. This document explains the differences between the tiers and how to choose the right one for your workload.
Available Access Tiers
Azure Blob Storage provides the following access tiers:
- Hot Tier: Optimized for frequently accessed data. This tier offers the lowest latency access to data and the highest costs.
- Cool Tier: Optimized for infrequently accessed data. Data in the cool tier is available with slightly higher latency than the hot tier, but at a lower storage cost.
- Archive Tier: Optimized for rarely accessed data that can tolerate hours of retrieval time. This tier offers the lowest storage costs but the highest retrieval costs and latency.
Access Tier Characteristics
Here's a comparison of the key characteristics across the different access tiers:
| Characteristic | Hot Tier | Cool Tier | Archive Tier |
|---|---|---|---|
| Data Accessibility | Immediate | Within hours (typically 1-12 hours for retrieval) | Within hours (typically 1-12 hours for retrieval) |
| Storage Cost | Highest | Medium | Lowest |
| Access Cost (Read/Write) | Lowest | Medium | Highest |
| Minimum Storage Duration | None | 30 days | 180 days |
Note on Minimum Durations
If you move data to the Cool tier and then delete or rehydrate it before 30 days, you will be charged for the full 30 days of storage. Similarly, moving data to Archive tier and deleting or rehydrating it before 180 days will incur charges for the full 180 days.
When to Use Each Tier
Hot Tier
Use the Hot tier for data that is:
- Actively being used or frequently accessed.
- Required for immediate access.
- Examples: Website content, frequently used application data, real-time analytics.
Cool Tier
Use the Cool tier for data that is:
- Infrequently accessed (less than once a month).
- Tolerant of slightly higher access latency.
- Examples: Backups, older log files, disaster recovery data.
Archive Tier
Use the Archive tier for data that is:
- Rarely accessed (less than once a year).
- Must be retained for compliance or archival purposes.
- Tolerant of long retrieval times (hours).
- Examples: Long-term archival of historical data, compliance archives.
Tip for Cost Optimization
Consider using Azure Blob Storage lifecycle management policies to automatically transition data between tiers based on access patterns and age. This can help optimize costs without manual intervention.
Managing Access Tiers
You can set the access tier for a blob when you upload it, or you can change the tier of an existing blob. You can perform these operations using:
- Azure Portal
- Azure CLI
- Azure PowerShell
- Azure Storage SDKs
Setting Access Tier with Azure CLI Example
az storage blob set-tier --account-name --container-name --name --tier Cool
Important Considerations
When rehydrating data from the Archive tier, there's a cost associated with the retrieval operation and it can take several hours. Plan your rehydration strategy carefully.
Conclusion
Azure Blob Storage access tiers provide a flexible and cost-effective way to manage your data. By understanding your data access patterns, you can choose the appropriate tier to minimize costs while ensuring data availability and performance.