Blob access tiers
What it is
Access tiers let you optimize blob storage cost by the expected access frequency. Hot = frequent, Cool = infrequent, Cold = rarely, Archive = long-term rarely-accessed. The tier trades storage cost against access/retrieval cost and latency.
Why it exists
Most data (‘unstructured/marketing/backup/compliance’) is accessed rarely once written. Paying full hot-tier price for it wastes money. Tiers align cost with access patterns.
The tiers
- Hot — high storage cost, near-zero retrieval, lowest latency. Default for new blobs.
- Cool — lower storage, higher access cost + minimum 30-day storage period. For data inactive >30 days.
- Cold (added 2024) — cheaper storage than cool, higher access cost + 90-day minimum. Rarely accessed.
- Archive — lowest storage cost, offline: you must rehydrate (move back to hot/cool) before reading, which takes hours. Min storage 180 days; not for GPv1.
Tier can be set at the storage-account default or per blob. Movement is automatic via lifecycle management rules (based on age, last-modified) or manually with az storage blob set-tier.
How it fits (diagram)
Exam notes
- Archive tiers are offline — no immediate read; reheat (rehydrate) required.
- Lifecycle management automates tier moves + deletion by rules (e.g., cool after 30d, archive after 90d, delete after 365d).
- Cool/cold/archive carry minimum storage-duration penalties if deleted early.
- Account-level default tier vs per-blob tier: per-blob wins.
Related
blob-storage · storage-account · storage-performance · immutable-storage
📘 Source: Microsoft Learn — Access Tier