Understanding the Archive Tier of Azure Storage Accounts

Introduction

Azure Storage provides various access tiers to optimize costs and performance based on data usage. One such tier is the Archive Tier, which is designed for infrequently accessed data that needs long-term storage at the lowest cost. Let’s break it down in simple terms.

What is the Archive Tier?

The Archive Tier is a storage option within Azure Blob Storage that allows you to store data at a very low cost. However, it comes with a trade-off: higher latency and costs to access or modify the data. It’s perfect for data that:

• You don’t need to access regularly.
• You want to keep for compliance, backup, or historical analysis.
• Can tolerate retrieval delays of several hours.

Key Features of the Archive Tier

1. Cost-Effectiveness

• The storage cost is the lowest among Azure storage tiers.
• The retrieval cost is higher, meaning you pay more when you want to read or modify the data.

2. High Latency

• Data in the Archive Tier is not immediately accessible.
• Retrieving data may take several hours as it is "rehydrated" (moved to a Hot, Cool, or Cold tier for access).

3. Data Security

• Data in the Archive Tier is encrypted and replicated, ensuring security and durability.

4. Use Cases

• Long-term backups (e.g., annual reports or logs).
• Historical datasets (e.g., old research data).
• Compliance and archival requirements (e.g., regulatory documents).

Rehydrate Data: Priorities Matter

If you need to access data stored in the Archive Tier, you must rehydrate it by changing its tier to Hot, Cool, or Cold, depending on your access needs. The rehydration process can take several hours, and Azure offers two rehydration priorities to give you flexibility:

1. Standard Priority

   • Cost: Lower retrieval cost.
   • Speed: Rehydration can take up to 15 hours for blobs up to 50 GB. Larger blobs or those with higher concurrency may take longer.
   • Use Case: Ideal for planned or non-urgent data access where cost savings matter more than retrieval speed.

2. High Priority

   • Cost: Higher retrieval cost.
   • Speed: Rehydration typically completes within 1–5 hours for blobs up to 50 GB.
   • Use Case: Perfect for urgent scenarios where you need quicker access to data, such as responding to compliance audits or critical system recoveries.

How to Choose the Right Priority

Consider the following:

• Is the data needed urgently?
  If yes, opt for High Priority. If not, save on costs with Standard Priority.

• What’s the size of the data?
  Larger blobs or bulk retrievals may impact rehydration time for Standard Priority.

• Budget vs. Time Trade-off
  High Priority comes at a premium cost, so plan accordingly for budget-sensitive workloads.

Rehydration Steps

1. Use the Azure Portal, CLI, or Storage SDKs to change the tier of the blob.
2. Select the desired rehydration priority (Standard or High).
3. Wait for the rehydration process to complete before accessing your data.

Pros and Cons of the Archive Tier

When to Avoid the Archive Tier

Avoid using the Archive Tier if:

• You need frequent access to the data.
• You cannot tolerate delays in data retrieval.
• Your use case involves frequent writes or modifications.

For frequently accessed data, consider the Hot, Cool, or Cold tiers instead.

Final Thoughts

The Archive Tier is an excellent option for storing data you rarely need to access but must retain for long periods. By leveraging Azure Blob Storage's tiering capabilities, you can optimize storage costs while ensuring your data is safe and durable.

When using the Archive Tier, always plan for retrieval costs and time delays. This way, you can balance cost savings with operational efficiency.