This chapter covers Azure Blob Storage, Azure's primary service for storing unstructured data at scale. AZ-900 tests this under objective 2.4, "Describe Azure storage services."
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A simple way to picture Azure Blob Storage
A traditional filing cabinet organizes documents in a strict folder structure, with specific rules about what goes where. A warehouse full of labeled boxes works differently — you can store almost anything in a box (a photo, a video, a document, a backup file), label it, and retrieve it later by its label, without the box needing to fit into a rigid folder hierarchy. Azure Blob Storage works like that warehouse: it stores large amounts of unstructured data — photos, videos, documents, backups, log files — as individual "blobs," identified and retrieved by name, without requiring the data to fit a specific structured format.
What Blob Storage is
Azure Blob Storage is a service for storing large amounts of unstructured data — data that doesn't follow a specific structured format, like images, videos, documents, log files, and backups. Data is stored as "blobs" (binary large objects) within containers, which are similar in concept to folders.
How it's organized
Blob Storage uses a flat structure of storage accounts, containing containers, which contain individual blobs. While blob names can include forward slashes to simulate a folder-like structure, the underlying organization is simpler than a traditional file system's nested folder hierarchy.
Access tiers
Blob Storage offers different access tiers based on how frequently data is accessed: a hot tier for frequently accessed data, a cool tier for infrequently accessed data kept for at least a short period, and an archive tier for rarely accessed data kept for extended periods, generally at progressively lower storage cost but with different retrieval characteristics for less-frequently-accessed tiers.
Common use cases
Blob Storage is commonly used for serving images or documents directly to a website, storing backup and disaster-recovery data, storing data for big-data analytics, and storing log files or other data generated by applications.
How it compares to other storage types
Blob Storage is specifically for unstructured data. Structured, relational data typically belongs in a database service (like Azure SQL Database, covered in its own chapter); Azure Files (also covered separately) is a better fit when a traditional shared file system is specifically needed.
Create a storage account
A storage account is created first, serving as the top-level container for blob storage (and other storage services) within Azure.
Create a container
A container is created within the storage account to organize related blobs, similar in concept to a folder.
Upload blobs
Individual files (images, documents, backups, and so on) are uploaded as blobs within the container.
Choose an appropriate access tier
Based on how frequently the data will be accessed, an access tier (hot, cool, or archive) is chosen to balance storage cost against retrieval characteristics.
A media company stores video files for its streaming service in Blob Storage, using the hot tier for actively watched content and the cool or archive tier for older content that's rarely accessed but still needs to be retained.
A separate company stores its nightly backup files in Blob Storage's archive tier, since those backups are rarely accessed but need to be retained for compliance purposes — taking advantage of the lower storage cost for infrequently accessed data, while accepting that retrieving archived data may take longer or work differently than retrieving hot-tier data.
Objective 2.4 expects candidates to understand what Blob Storage is used for (unstructured data), its basic organization (storage account, container, blob), and the purpose of access tiers.
A common wrong answer is describing Blob Storage as suited for structured, relational data — that belongs in a database service instead. Another common trap is assuming all access tiers cost and behave identically — hot, cool, and archive tiers differ in storage cost and retrieval characteristics, generally trading lower storage cost for less immediate retrieval for colder tiers.
Stable terms: Blob Storage, container, blob, hot/cool/archive tier. Recognizing Blob Storage as Azure's unstructured data storage service, distinct from Azure Files or database services, is a frequently tested distinction.
Memory trick: Blob Storage = unstructured data (images, videos, backups, logs), organized as storage account → container → blob, with tiers trading cost against how quickly you need to retrieve the data.
Azure Blob Storage stores large amounts of unstructured data — images, videos, documents, backups, and logs.
Blob Storage is organized as storage account → container → blob, a flatter structure than a traditional file system.
Access tiers (hot, cool, archive) let organizations balance storage cost against how frequently data needs to be retrieved.
Structured, relational data belongs in a database service, not Blob Storage.
These come up on the exam all the time. Here's how to tell them apart.
Azure Blob Storage
Flat structure: storage account → container → blob
Optimized for large amounts of unstructured data
Accessed via APIs and Azure tools
Tiered pricing based on access frequency
Traditional File System
Nested folder hierarchy
General-purpose file storage
Accessed directly through an operating system
Typically a single consistent cost structure
Mistake
Blob Storage is meant for structured, relational data.
Correct
Blob Storage is specifically for unstructured data like images, videos, documents, and backups. Structured, relational data typically belongs in a database service like Azure SQL Database.
Mistake
All Blob Storage access tiers behave and cost the same.
Correct
Hot, cool, and archive tiers differ in storage cost and retrieval characteristics — generally, colder tiers cost less to store data but have different (often slower or less immediate) retrieval characteristics.
Mistake
Blob Storage requires a traditional nested folder structure like a file system.
Correct
Blob Storage uses a flatter structure of storage accounts, containers, and blobs. Folder-like organization can be simulated using naming conventions, but it isn't a true nested file system.
It's used for storing large amounts of unstructured data — images, videos, documents, backup files, and logs. Data is stored as individual 'blobs' within containers, organized under a storage account.
Hot, cool, and archive tiers let you balance storage cost against how frequently data is accessed. Hot suits frequently accessed data; cool suits infrequently accessed data kept for a short period; archive suits rarely accessed data kept for longer periods, generally at lower storage cost but with different retrieval characteristics.
No — Blob Storage is designed for unstructured data. Structured, relational data should use a dedicated database service like Azure SQL Database instead, which is built for that kind of structured querying and relationships.
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