Azure Blob Storage

Azure Blob Storage is the most widely used storage service in Azure. It is designed to store massive amounts of unstructured data — data that does not fit into a table with rows and columns. Images, videos, PDFs, log files, backups, and audio files are all examples of unstructured data that Blob Storage handles perfectly.

"Blob" stands for Binary Large Object. It simply means any file — regardless of type — that is stored as a chunk of binary data.

Blob Storage Structure

Blob Storage is organized in a three-level hierarchy:

Diagram – Blob Storage Hierarchy

  Storage Account: mystorageaccount
  │
  ├── Container: profile-photos          ← Like a folder/bucket
  │   ├── user1.jpg                      ← Blob (file)
  │   ├── user2.png
  │   └── user3.jpg
  │
  ├── Container: documents
  │   ├── invoice-001.pdf
  │   ├── contract-2024.pdf
  │   └── reports/
  │       └── q1-report.xlsx
  │
  └── Container: backups
      ├── db-backup-2024-01-01.bak
      └── db-backup-2024-01-02.bak

Types of Blobs

Azure Blob Storage offers three types of blobs, each optimized for different scenarios:

Block Blob

The most common blob type. It stores data as individual blocks that are assembled into a single blob. Designed for text and binary files — images, videos, documents, backups. Can store up to 190.7 TB per blob.

Append Blob

Optimized for append operations — data can only be added to the end, never modified in the middle. Perfect for logging scenarios where records are continuously added to a log file.

Example: Application logs where each new log entry is appended to the end of the file.

Page Blob

Optimized for random read and write operations in 512-byte pages. Used internally by Azure for Virtual Machine disk files (VHDs). Can store up to 8 TB per blob.

Container Access Levels

Each container has an access level setting that controls whether blobs are publicly accessible or require authentication:

Blob Lifecycle Management

Data naturally becomes less valuable over time. A backup from yesterday is critical; a backup from two years ago is rarely accessed. Lifecycle management policies automatically move or delete blobs based on age to reduce storage costs.

Example Lifecycle Policy

  Policy: BackupLifecycle

  Rule 1: Move to Cool tier after 30 days (data older than 30 days)
  Rule 2: Move to Archive tier after 90 days
  Rule 3: Delete blobs after 365 days

  Timeline for a backup file created on Day 0:
  ┌──────────┬──────────┬──────────────┬────────────┐
  │  Day 0   │  Day 30  │   Day 90     │  Day 365   │
  │  HOT     │  COOL    │   ARCHIVE    │  DELETED   │
  │ (Active) │ (Cheaper)│  (Cheapest)  │            │
  └──────────┴──────────┴──────────────┴────────────┘

Static Website Hosting with Blob Storage

Azure Blob Storage can host a static website — an HTML/CSS/JavaScript website with no server-side code. This is an extremely cost-effective way to host simple websites, landing pages, or documentation sites.

How to Enable Static Website Hosting

1. Go to the storage account → Static website (under Data management)
2. Toggle Enabled
3. Set the Index document name (e.g., index.html)
4. Set the Error document path (e.g., 404.html)
5. Upload website files to the automatically created $web container
6. The website is accessible via the URL shown (e.g., https://mystorageaccount.z13.web.core.windows.net)

Uploading and Accessing Blobs

Using Azure Portal

Open the storage account → Containers → Open the container → Upload button → Browse and select files. Simple drag-and-drop is also supported.

Using Azure CLI

  # Upload a file to blob storage
  az storage blob upload \
    --account-name mystorageaccount \
    --container-name documents \
    --name invoice.pdf \
    --file /local/path/invoice.pdf

  # List all blobs in a container
  az storage blob list \
    --account-name mystorageaccount \
    --container-name documents \
    --output table

  # Download a blob
  az storage blob download \
    --account-name mystorageaccount \
    --container-name documents \
    --name invoice.pdf \
    --file /local/downloads/invoice.pdf

Using Azure Storage Explorer

Azure Storage Explorer is a free desktop application (Windows, macOS, Linux) that provides a graphical interface for managing storage accounts. It supports drag-and-drop uploads, folder navigation, and SAS token generation — no command line needed.

Blob Storage Pricing Factors

• Storage used: Charged per GB stored per month, varies by access tier (Hot, Cool, Cold, Archive)
• Operations: Charged per 10,000 read or write operations
• Data transfer: Inbound (upload to Azure) is free; outbound (download from Azure) is charged per GB
• Redundancy: GRS costs more than LRS
• Lifecycle transitions: Moving a blob from Hot to Archive is a one-time operation charge, but saves on ongoing storage cost

Key Takeaways

• Azure Blob Storage stores unstructured data — any file type and any size.
• Blobs are organized inside containers, which are inside storage accounts.
• Three blob types exist: Block Blob (general files), Append Blob (log files), Page Blob (VM disks).
• Container access levels control whether blobs are private (authenticated only) or publicly readable.
• Lifecycle management policies automate moving blobs between Hot, Cool, Cold, and Archive tiers to reduce cost.
• Blob Storage can host a static website (HTML/CSS/JS) at very low cost.