Blob Types in Azure Storage
Azure Blob Storage is a cloud object storage solution for storing large amounts of unstructured data, such as text or binary data. Blobs can be accessed from anywhere in the world via HTTP or HTTPS. Blob storage can be used to serve images or documents directly to a browser, store files for distributed access, stream video and audio, store data for backup and restore, disaster recovery, and data archiving.
Blob storage contains three types of blobs:
Block Blobs
Block blobs are optimized for storing large amounts of unstructured data that can be segmented into 50 MB blocks. They are ideal for:
- Serving images or documents directly to a browser.
- Storing files for distributed access.
- Streaming video and audio files.
- Storing data for backups, restore, disaster recovery, and archiving.
A single block blob can be up to approximately 190.7 TiB in size, composed of blocks of up to 4.75 MiB each. The maximum size of a block blob is determined by the number of blocks. A block blob can contain a maximum of 50,000 blocks.
Key Characteristics:
- Immutable once written, unless updated with new blocks or replaced entirely.
- Optimized for sequential reads.
- Supports incremental writes.
Append Blobs
Append blobs are optimized for append operations, such as logging data. They are ideal for scenarios where data is written sequentially and infrequently, such as:
- Logging data from virtual machines.
- Logging data from application instances.
- Tracking activity.
Like block blobs, append blobs are made up of blocks. However, blocks in an append blob can only be added to the end. You cannot modify or delete an existing block in an append blob.
Key Characteristics:
- Optimized for append operations.
- Cannot be modified or deleted after writing, only appended to.
- Each block can be up to 4 MiB in size.
- A single append blob can contain a maximum of 50,000 blocks.
Page Blobs
Page blobs are optimized for random read and write operations. They are ideal for:
- Storing virtual hard disk (VHD) files for Azure virtual machines.
- Storing data that needs to be frequently updated, such as databases or filesystems.
Page blobs consist of pages, each up to 512 bytes in size. A page blob can be up to 8 TiB in size. A page blob can store up to 1,048,560 pages, and each page can be written to independently.
Key Characteristics:
- Optimized for random read and write operations.
- Pages can be updated independently.
- Efficient for storing structured data that requires random access.
Choosing the Right Blob Type
The choice of blob type depends heavily on your specific use case:
- For general-purpose storage of unstructured data, including media files, documents, and backups, use block blobs.
- For logging scenarios where you are writing data sequentially and need to append records, use append blobs.
- For storing virtual machine disk images or other structured data requiring frequent random read/write operations, use page blobs.
Understanding these distinctions will help you optimize your Azure Storage solution for performance, cost, and functionality.
For more detailed information on using each blob type, refer to the official Azure Storage documentation.