Azure Blob Storage: Files in the Cloud
Blob storage is Azure's service for storing massive amounts of unstructured data — images, videos, backups, and data lake files. It's one of the most-used Azure services.
What is Azure Blob Storage?
Blob Storage is like a massive, infinitely expandable digital warehouse.
You can throw anything in — photos, videos, backups, log files, CSVs, PDFs. There’s no limit to how much you can store. And unlike a database, you don’t need to define a schema or structure. Just upload files and access them via a URL.
”Blob” stands for Binary Large Object — a fancy name for “any file.”
Blob Storage hierarchy
Storage Account (unique namespace)
└── Container (like a folder)
├── Blob (photo.jpg)
├── Blob (backup-2026-04.sql)
└── Blob (sales-data.parquet)- Storage account: Top-level namespace with a globally unique name (e.g.,
freshmartstorage) - Container: A grouping for related blobs (like a folder, but flat — no nested folders by default)
- Blob: The actual data — any file type, up to hundreds of TB per blob
Types of blobs
| Type | Use Case | Example |
|---|---|---|
| Block blobs | General-purpose files. Most common type. | Images, videos, documents, data files |
| Append blobs | Optimised for append operations (adding data to the end). | Log files, audit trails |
| Page blobs | Optimised for random read/write operations. | Virtual hard disks (VHDs) for Azure VMs |
For DP-900, focus on block blobs — they’re what you’ll encounter most.
Access tiers
Not all data is accessed equally. Azure lets you choose a tier to balance cost vs access speed:
| Feature | Hot | Cool | Cold | Archive |
|---|---|---|---|---|
| Designed for | Frequently accessed data | Infrequently accessed (30+ days) | Rarely accessed (90+ days) | Long-term archival (180+ days) |
| Storage cost | Highest | Lower | Lower still | Lowest |
| Access cost | Lowest | Higher | Higher | Highest (rehydration needed) |
| Example | Active website images | Monthly reports | Quarterly backups | 7-year compliance archives |
Jake’s example: CloudPulse stores data across tiers:
- Hot: Current customer avatars and active documents
- Cool: Last month’s log files (kept for troubleshooting)
- Archive: Database backups older than 1 year (kept for compliance)
Lifecycle management
Azure can automatically move blobs between tiers based on rules. For example:
- Move blobs to Cool if not accessed for 30 days
- Move blobs to Archive if not accessed for 180 days
- Delete blobs after 365 days
This is called lifecycle management — set it once and Azure handles the cost optimisation automatically.
Exam tip: Blob Storage scenarios
Common exam patterns:
- “Store images for a website” → Block blobs, Hot tier
- “Store log files that are always growing” → Append blobs
- “Store backups kept for compliance, rarely accessed” → Block blobs, Archive tier
- “Store VM virtual hard disks” → Page blobs
- “Automatically move old data to cheaper storage” → Lifecycle management policies
Flashcards
Knowledge check
Priya's FreshMart needs to store 5 years of scanned delivery receipts for compliance auditing. The receipts are rarely accessed — maybe once a year during an audit. Which Blob Storage tier should she use?
Jake's application writes diagnostic log entries throughout the day, always adding new lines to the end of a log file. Which blob type is optimised for this pattern?
Next up: Azure Files & Table Storage — two more non-relational storage services with very different purposes.