Azure Storage Types: Blob, Files, Disks, Queue
Azure storage questions ask you to match the shape of the data and the way it is accessed to a service: objects and unstructured data go to Blob Storage, shared file shares to Azure Files, messages to Queue Storage, key-attribute records to Table Storage, and a virtual machine’s own volumes to managed disks. The decision rule is to name the access method first (HTTP object, SMB or NFS share, message, block volume) and only then pick the account type and access tier.
Match the data to the service
All of these except disks live inside a storage account, and the storage introduction lists them as the data services of the platform.
| If the requirement says | Service | Access method |
|---|---|---|
| Images, backups, logs, video, a data lake | Blob Storage (with Data Lake Storage capabilities if analytics) | REST over HTTP/HTTPS, SDKs, optionally SFTP or NFS 3.0 |
| A file share that servers or VMs mount, lift-and-shift of a file server | Azure Files | SMB, NFS, or REST |
| Decouple two application components with messages | Queue Storage | REST, messages up to 64 KB |
| Schemaless key/attribute records | Table Storage | REST |
| A volume for one VM, OS or data disk | Managed disks | Attached block device |
| SAN-style volumes for many compute resources over iSCSI | Elastic SAN | iSCSI |
Two details in that table are easy to lose. Managed disks are not accessed through a storage account you manage: Azure calls them “managed” because it abstracts the page blobs, containers and accounts behind them. And Microsoft’s documentation now describes Table Storage as part of the Azure Cosmos DB family of services, with Azure Cosmos DB for Table as the premium option; the exams still treat Table Storage as the cheap schemaless store.
Storage account types
You choose the account type when you create the account, and it cannot be changed afterwards; moving to a different type means creating a new account and copying the data. According to the storage account overview, the recommended types are:
| Account type | Services | Redundancy | Use it for |
|---|---|---|---|
| Standard general-purpose v2 | Blob (including Data Lake Storage), Queue, Table, Files | LRS, GRS, RA-GRS, ZRS, GZRS, RA-GZRS | The default for most scenarios |
| Premium block blobs | Block and append blobs | LRS, ZRS | High transaction rates, small objects, low latency |
| Premium file shares | Azure Files only | LRS, ZRS | High-performance shares; the type for NFS and SMB together |
| Premium page blobs | Page blobs only | LRS, ZRS | Random-access page blob workloads |
Premium accounts use SSDs. General-purpose v1 and the legacy Blob Storage account type are retired or being retired, with upgrade to v2 recommended, so a modern answer is rarely v1. Account names must be 3 to 24 characters, lowercase letters and digits only, and unique across Azure. Redundancy choices such as LRS versus ZRS are a separate topic: see storage redundancy explained.
Access tiers apply to block blobs
Tiers answer the cost question for data that cools over time. Setting a tier is only allowed on block blobs, not on append or page blobs.
| Tier | Online? | Minimum retention | Notes |
|---|---|---|---|
| Hot | Yes | None | Highest storage cost, lowest access cost; the default for a new v2 account |
| Cool | Yes | 30 days | Lower storage cost, higher access cost |
| Cold | Yes | 90 days | Rarely accessed but still needs fast retrieval |
| Archive | No (offline) | 180 days | Cheapest storage; rehydrate to read, which can take up to 15 hours |
Deleting or moving a blob before the minimum period triggers an early deletion charge. Archive cannot be the account’s default tier, and it is supported only on LRS, GRS and RA-GRS accounts, not on ZRS, GZRS or RA-GZRS. Lifecycle management rules move blobs between tiers automatically, but they cannot rehydrate an archived blob. Data in a premium block blob account cannot be tiered at all. These details come from the access tiers overview.
Worked example: five needs, five answers
A small publisher moves to Azure.
- Cover images and PDFs served to a website. Block blobs in a general-purpose v2 account, hot tier.
- Seven-year archive of old issues, read maybe once a year. Block blobs moved to archive by a lifecycle rule. Check the redundancy: archive rules out ZRS, so the account must be LRS, GRS or RA-GRS. Budget for hours of rehydration when an issue is requested.
- Editors’ shared drive mounted on Windows laptops. Azure Files over SMB; identity-based access if it must honor the company directory.
- Order processing hand-off between the web front end and a back-end worker. Queue Storage: the front end writes a message, the worker reads it. If messages exceed 64 KB, the design needs a different service.
- A database VM that needs its own fast volume. A managed disk attached to the VM. Not a file share, because only that VM uses it.
Which exams test this
| Exam | How the topic appears | Where on this site |
|---|---|---|
| AZ-900 | Describe Azure architecture and services (35 to 40%): compare storage services, describe access tiers, redundancy, account options and types, and file-moving tools such as AzCopy and Azure File Sync | Architecture and services explained |
| AZ-104 | Implement and manage storage (15 to 20%): create and configure accounts, Azure Files shares, Blob containers, tiers, soft delete, versioning and lifecycle management | Storage explained |
| AZ-305 | Design data storage solutions (20 to 25%): recommend a solution for semi-structured and unstructured data balancing features, performance and cost | Data storage explained |
| AZ-802 | Storage and file services: create and manage Azure file shares and Azure File Sync; manage storage for Windows Server VMs in Azure | Storage and file services explained |
| SC-500 | Minor: securing storage accounts (firewall, access) rather than choosing types | Storage, databases and networking explained |
How exam questions are built around this
- Protocol words decide. “SMB share”, “mounted drive” means Azure Files. “REST”, “static website”, “images” means Blob. “iSCSI” means Elastic SAN.
- “Lowest cost” plus “rarely accessed”. Look for a tier and a minimum-retention constraint. If the data must be readable within milliseconds, cool or cold, not archive.
- Archive plus ZRS. A scenario with zone redundancy and an archive requirement contains a conflict; the answer changes redundancy or avoids archive.
- “Change the account type.” Not possible in place; the answer is a new account and a copy (AzCopy). Upgrading v1 or legacy Blob to v2 is the one supported upgrade path.
- Access control is separate. Choosing a type is not the same as securing it; shared access signatures belong to SAS tokens and stored access policies, and network restriction to private endpoint vs service endpoint.
Practice questions
Question 1. A company needs a cloud file share that a group of Windows servers mount with SMB, replacing an on-premises file server. Which service fits?
- A. Blob Storage block blobs
- B. Queue Storage
- C. A managed disk
- D. Azure Files
Show answer
Answer: D
Azure Files provides managed file shares accessed over SMB (and NFS), which is what a mounted file-server replacement needs. Blob Storage holds objects accessed over REST, Queue Storage holds messages, and a managed disk is attached to a single VM rather than shared by many servers.
Question 2. Scanned contracts must be kept for ten years, are almost never read, and may be retrieved within a day when needed. The storage account currently uses ZRS. Which statement is correct?
- A. Use the archive tier, which requires an account with LRS, GRS or RA-GRS redundancy
- B. Use the archive tier and set it as the account default tier on the ZRS account
- C. Move the data to a premium block blob account and tier it to archive
- D. Use the cool tier because archive cannot be rehydrated within a day
Show answer
Answer: A
The archive tier is offline and cheapest, and rehydration can take up to 15 hours, which fits a one-day retrieval window. However, archive is supported only on LRS, GRS and RA-GRS accounts, so ZRS must be changed or the data placed in another account. Cool is not the cheapest for long retention, archive cannot be the default account tier, and premium block blob accounts cannot be tiered.
Go deeper
- Introduction to Azure Storage (Microsoft Learn)
- Storage account overview (Microsoft Learn)
- Access tiers for blob data (Microsoft Learn)
- Related: storage redundancy explained, Azure Backup and Site Recovery, choosing an Azure compute service