Last updated: May 2026

Azure Storage Beginner AZ-104 ⏱ 11 min read

Blob Access Tiers

Not all data is accessed equally. A photo you just uploaded gets viewed constantly. A three-year-old compliance report might never be touched again. Azure Blob Storage's access tiers let you optimise storage costs by matching the tier to the access frequency — paying less for data you rarely need, and paying more (but getting fast access) for data you use every day.

What you'll learn The four access tiers — Hot, Cool, Cold, and Archive · Cost trade-offs between tiers · Minimum retention periods and early deletion fees · How to set the tier at account and blob level · Changing tiers via CLI · Rehydrating from Archive · Lifecycle management overview

Table of Contents

What Are Access Tiers?
Hot Tier
Cool Tier
Cold Tier
Archive Tier
Side-by-Side Comparison
Setting Access Tiers
Rehydrating from Archive
Choosing the Right Tier
Practice Questions

What Are Access Tiers?

Azure Blob Storage access tiers are a way to balance storage cost against access cost. The pattern is consistent across all tiers:

Lower storage cost = Higher access cost + longer retrieval time
Higher storage cost = Lower access cost + instant retrieval

Choose based on how often your data is accessed. Move infrequently accessed data to cheaper tiers to save significantly on storage costs.

Hot Tier

The Hot tier is optimised for data that is accessed frequently. It has the highest storage cost but the lowest access cost and instant retrieval.

Access frequency: Data accessed regularly or daily
Retrieval: Immediate
Minimum retention: None
Best for: Active website assets, application data being read/written regularly, recently uploaded files

💡

Default Tier Hot is the default tier for new blobs unless you specify otherwise. The storage account also has a default access tier (Hot or Cool) that applies to all new blobs unless overridden at the blob level.

Cool Tier

The Cool tier is optimised for data that is infrequently accessed and stored for at least 30 days. Storage cost is lower than Hot, but access and retrieval costs are higher.

Access frequency: Accessed less than once a month
Retrieval: Immediate (same as Hot)
Minimum retention: 30 days (early deletion fee applies)
Best for: Short-term backups, older application data, disaster recovery copies used rarely

⚠️

Early Deletion Fee If you delete or move a blob from Cool tier within 30 days of setting it to Cool, you're charged for the remaining days. Always factor in the minimum retention period when planning tier transitions.

Cold Tier

The Cold tier (introduced in 2023) sits between Cool and Archive. It offers lower storage costs than Cool but higher access costs, with a 90-day minimum retention period.

Access frequency: Rarely accessed — a few times per year
Retrieval: Immediate (milliseconds)
Minimum retention: 90 days
Best for: Long-term backups, compliance archives that occasionally need access, older data that must be retrievable quickly

Archive Tier

The Archive tier is the cheapest storage option — designed for data that is rarely (if ever) accessed and can tolerate several hours of retrieval time. Data in Archive is stored offline.

Access frequency: Almost never — regulatory or compliance archives
Retrieval: Hours (must be "rehydrated" before access)
Minimum retention: 180 days
Best for: Long-term compliance data, legal archives, old backups that must be kept but rarely accessed

ℹ️

Archive = Offline Storage Blobs in Archive tier are stored offline — you cannot read them directly. You must first "rehydrate" them (move to Hot or Cool) which takes 1–15 hours depending on the priority setting. Only then can you access the data.

Side-by-Side Comparison

Tier	Storage Cost	Access Cost	Retrieval Time	Min Retention
Hot	Highest	Lowest	Immediate	None
Cool	Medium	Medium	Immediate	30 days
Cold	Low	High	Immediate	90 days
Archive	Lowest	Highest	Hours	180 days

Setting Access Tiers

Tiers can be set at two levels:

Account level — Default tier for all new blobs (Hot or Cool only)
Blob level — Override for individual blobs (Hot, Cool, Cold, or Archive)

Azure CLI Set blob access tier

# Set a blob to Cool tier
az storage blob set-tier \
  --account-name mystorageaccount2026 \
  --container-name backups \
  --name old-backup.bak \
  --tier Cool \
  --auth-mode login

# Set a blob to Archive tier
az storage blob set-tier \
  --account-name mystorageaccount2026 \
  --container-name archives \
  --name compliance-2020.pdf \
  --tier Archive \
  --auth-mode login

Rehydrating from Archive

To access a blob in Archive tier, you must first rehydrate it — move it to Hot or Cool tier. There are two rehydration priorities:

Priority	Time	Cost	Use When
High priority	Under 1 hour (for blobs < 10 GB)	Higher	Urgent retrieval needed
Standard priority	Up to 15 hours	Lower	Non-urgent retrieval

Azure CLI Rehydrate a blob from Archive to Hot

# Rehydrate with standard priority (up to 15 hours)
az storage blob set-tier \
  --account-name mystorageaccount2026 \
  --container-name archives \
  --name compliance-2020.pdf \
  --tier Hot \
  --rehydrate-priority Standard \
  --auth-mode login

Choosing the Right Tier

Data Example	Access Pattern	Recommended Tier
Profile pictures on a social app	Accessed every page load	Hot
Last month's backups	Rarely accessed, might restore if needed	Cool
6-month-old application data	Very rarely accessed	Cold
7-year compliance archive	Almost never — legal requirement only	Archive

💡

AZ-104 Exam Tip Know all four tiers and their retrieval times. Hot = immediate + expensive storage. Archive = hours to retrieve + cheapest storage. Know the minimum retention periods: Cool = 30 days, Cold = 90 days, Archive = 180 days. Archive blobs must be rehydrated before they can be accessed.

📝 Practice Questions

Click an option to check your answer. AZ-104 style questions.

Q1. A company stores 7-year-old compliance documents that are legally required to be retained but almost never accessed. Which access tier is most cost-effective?

A Hot

B Cool

C Cold

D Archive

Q2. How long does it take to access a blob stored in Archive tier?

A Immediately — same as Hot tier

B A few minutes

C Up to 15 hours (standard priority) or under 1 hour (high priority)

D 1–3 days

Q3. What is the minimum retention period for the Cool access tier?

A 30 days

B 90 days

C 180 days

D No minimum retention period

Q4. Can blobs in Archive tier be read directly without any special process?

A Yes — they can be read immediately, just like Hot tier blobs

B Yes — but only with additional authentication

C No — they must first be rehydrated (moved to Hot or Cool), which takes hours

D Yes — using a special archive API endpoint

Q5. Which access tier provides the lowest storage cost but the highest access and retrieval cost?

A Hot

B Cool

C Cold

D Archive

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