Moving Azure Blob Storage from Hot to Archive: The Intermediate Tier Requirement

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The Problem

You've configured a lifecycle management rule to move blobs directly from Hot to Archive tier, but nothing happens. Your blobs stubbornly remain in the hot tier, racking up storage costs.

Why? Azure Blob Storage doesn't support direct transitions from hot to archive.

The Solution: Use an Intermediate Tier

Azure requires blobs to pass through either the Cool or Cold tier before reaching archive. This is by design and applies to all lifecycle management policies.

Valid Transition Paths:

  • Hot → Cool → Archive ✓
  • Hot → Cold → Archive ✓
  • Hot → Cool → Cold → Archive ✓
  • Hot → Archive ✗

Implementation

Configure your lifecycle management rule with two transitions:

Rule: Archive old backups

IF base blobs were:
  Last modified more than 1 days ago
THEN:
  Move to cold storage

IF base blobs were:
  Last modified more than 2 days ago
THEN:
  Move to archive storage
  ☑ Skip blobs rehydrated in last 7 days

Cool vs. Cold: Which to Choose?

  • Cool tier: Better for data accessed occasionally (minimum 30-day retention)
  • Cold tier: Better for rarely accessed data (minimum 90-day retention, lower storage cost)

For most backup and archival scenarios, Cold is the better intermediate tier since it aligns with archival use cases and costs less.

Best Practices

  1. Plan your timeline: Consider minimum retention periods to avoid early deletion fees
  2. Check rehydration settings: Always enable "Skip blobs rehydrated in last X days" to prevent immediate re-archival
  3. Monitor costs: The intermediate tier will incur brief storage costs, but this is negligible compared to keeping everything in hot tier
  4. Test first: Validate your policy on a test container before applying to production

The Bottom Line

Direct hot-to-archive transitions aren't supported in Azure. Add a cool or cold tier intermediate step, and your lifecycle management policies will work as expected.

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