Azure Blob Storage Access Tiers

Last updated: October 26, 2023

Azure Blob Storage offers several access tiers to optimize costs based on data access patterns. These tiers allow you to store blob data affordably and efficiently by choosing the most appropriate tier for your workload.

Understanding Access Tiers

Blob storage access tiers provide a way to optimize storage costs by defining how frequently data is accessed. Choosing the right tier can significantly reduce your overall storage expenses.

Available Access Tiers:

Hot Tier

Optimized for frequently accessed data.

Lowest access latency
Highest transaction costs
Best for active data

Ideal for: Frequently read or modified data, such as website content, active application data, and temporary backups.

Cool Tier

Optimized for infrequently accessed data or data that needs to be stored for at least 30 days.

Higher access latency than Hot tier
Lower transaction costs than Hot tier
Lower storage costs than Hot tier

Ideal for: Data that is accessed infrequently but requires rapid availability when needed, such as recent backups, disaster recovery data, or older logs.

Archive Tier

Optimized for rarely accessed data that can tolerate longer retrieval times (hours).

Highest access latency (hours)
Lowest storage costs
Highest transaction costs for retrieval
Data must be rehydrated before reading

Ideal for: Data that is rarely accessed and can tolerate hours of retrieval time, such as long-term backups, compliance archives, or historical data for infrequent analysis.

Choosing the Right Tier

The best access tier depends on your specific data access patterns and business requirements. Consider the following factors:

Frequency of Access: How often do you need to read or write the data?
Latency Requirements: How quickly does the data need to be available when requested?
Cost Sensitivity: What is your budget for storage and access operations?
Data Retention Period: How long do you plan to store the data?

Tiering Best Practices

To optimize costs and performance, you can:

Use Lifecycle Management: Automate the transition of blobs between tiers based on rules you define (e.g., move data from Hot to Cool after 30 days, then to Archive after 180 days).
Monitor Access Patterns: Regularly review your data access logs to understand how your data is being used and adjust your tiering strategy accordingly.
Consider Retrieval Costs: Be mindful of the retrieval costs associated with the Cool and especially the Archive tiers, as frequent retrievals can negate the savings in storage costs.

Access Tier Pricing

Pricing varies by tier. Here's a general overview (refer to the official Azure Pricing Page for exact details):

Tier	Storage Cost	Access Cost (Read)	Access Cost (Write)	Retrieval Latency	Minimum Retention
Hot	Highest	Highest	Low	Milliseconds	N/A
Cool	Medium	Medium	Medium	Milliseconds	30 days
Archive	Lowest	Highest	Highest	Hours	180 days

Example Scenarios

Scenario 1: Active Website Content - Data is frequently accessed by users. The Hot tier is the most suitable.
Scenario 2: Monthly Backups - Data is backed up monthly and rarely accessed, but needs to be readily available for restore. The Cool tier is a good fit.
Scenario 3: Archival Records - Compliance requires storing old business records for years, with very infrequent access. The Archive tier offers the lowest storage cost.

By leveraging Azure Blob Storage access tiers effectively, you can achieve significant cost savings while ensuring your data is available when and how you need it.