4.1.1. Azure Blob Storage

💡 First Principle: Azure Blob Storage is a massively scalable object storage service for unstructured data. Think of it as infinite shelf space where you can store any file—the service doesn't care what's inside. Its core purpose is providing a cost-effective and durable solution for storing vast amounts of data like documents, images, videos, and backups.

What It Is: A service for storing large amounts of unstructured data (data that doesn't adhere to a particular data model or definition), such as text or binary data.

Blob Types

💡 First Principle: Blob Storage offers three types of blobs optimized for different storage and access patterns—choosing the wrong type creates unnecessary costs or performance problems.

• Block Blobs: Optimized for storing discrete files (images, documents, videos). The most common type. Uploaded in blocks.
• Append Blobs: Optimized for append operations. New data can only be added to the end. Ideal for logging scenarios.
• Page Blobs: Optimized for random read/write operations. Used for virtual machine disks (VHDs).

Access Tiers

💡 First Principle: Access tiers allow you to balance storage costs against access costs and latency requirements, matching the lifecycle of your data. The trade-off is simple: cheaper storage means more expensive (or slower) access.

Visual: Blob Storage Access Tiers & Lifecycle

Lifecycle Management and Soft Delete

Lifecycle management policies automate what would otherwise be manual housekeeping. You write rules against a blob's age — typically last-modified date — and Azure applies them for you:

• Transition blobs to a cooler tier (Hot → Cool → Cold → Archive) as they age.
• Delete blobs entirely after a retention period.
• Scope rules to a prefix or blob index tag so different folders age differently.

A lifecycle policy moves and deletes data. It does not encrypt, replicate, or convert file formats — a Parquet file stays Parquet whichever tier it sits in.

Soft delete is the safety net underneath all of this. When enabled, a deleted blob (or snapshot, or container) is retained for a configured number of days and can be restored, which protects you from an accidental delete or an over-eager lifecycle rule.