Azure Blob Storage Types Explained
Azure Blob Storage offers flexible, scalable object storage for unstructured data. Whether you’re archiving documents, storing logs, or hosting VM disks, Azure provides three blob types—Block Blobs, Append Blobs, and Page Blobs—each designed for different access patterns and workloads.
Choosing the correct blob type ensures cost-effective performance and optimal application behavior. Let’s break down what each type is, how it works, and when to use it.
What Are Block Blobs?
Block Blobs are optimized for uploading large files like images, videos, documents, or backups. Data is uploaded in blocks (each up to 4000 MiB), which can be uploaded in parallel for faster performance. Once uploaded, these blocks are committed together as a single blob.
- Efficient for streaming and storage of large, unstructured files.
- Supports parallel uploads and block-level updates.
- Supports up to 190.7 TiB of total blob size.
- Perfect for backups, media storage, and large file ingestion.
What Are Append Blobs?
Append Blobs are designed for scenarios where data needs to be continuously added, without modifying existing content. They’re ideal for log files, audit trails, telemetry data, and other append-only scenarios.
Unlike block blobs, append blobs don’t allow modification or deletion of individual blocks once written. New data is always written sequentially at the end, preserving historical accuracy.
- Append-only—each write appends new data.
- Ensures sequential integrity for event and telemetry capture.
- Supports up to 195 GB in total size.
- Great for diagnostics and immutable logging.
What Are Page Blobs?
Page Blobs are used for workloads that require high IOPS and random read/write access—such as virtual machine disks. Page blobs store data in 512-byte aligned pages and allow modification at the byte level, unlike append or block blobs.
- Used for Azure Virtual Machines (OS and data disks).
- Enables high-performance disk-based operations.
- Supports random access patterns and frequent updates.
- Maximum size: 8 TiB.
Premium Block Blob Accounts
If performance is critical, Premium Block Blob Storage provides low-latency and high-throughput capabilities. Ideal for scenarios like real-time analytics or streaming services, this tier delivers performance enhancements compared to the standard storage tiers.
Blob Type Comparison Table
| Blob Type | Best Use Case | Max Size | Access Pattern | Write Behavior | Modifiability |
|---|---|---|---|---|---|
| Block Blob | Large file uploads, backups, media | Up to 190.7 TiB | Random read/write | Upload in blocks, can be parallelized | Blocks can be replaced before commit |
| Append Blob | Audit logs, telemetry, time-based data | Up to 195 GB | Sequential appends | Only append blocks | No overwrite; append-only |
| Page Blob | Virtual machine disks, IOPS-intensive workloads | Up to 8 TiB | Random read/write | Written in 512-byte aligned pages | Individual pages can be modified |
Want to dive deeper? Explore each blob type in more detail with our dedicated guides: Block Blobs, Append Blobs, Page Blobs, and Premium Blob Storage.