Azure Blob Storage is a cloud-based object storage solution that allows you to store and manage large amounts of unstructured data. There are three types of blobs in Azure Blob Storage: block blobs, page blobs, and append blobs. Each of these blob types has different characteristics and is optimised for different use cases.
- Block Blobs: Block blobs are the most commonly used type of blob in Azure Blob Storage. They are designed for storing large files, up to around 4.75 TB in size, and are optimised for sequential access. Block blobs can be written and read in chunks, making them suitable for streaming large media files, such as videos or music. Block blobs are also ideal for storing unstructured data, such as text documents or images.
Block blobs are composed of smaller blocks that are uploaded to Azure Blob Storage and then assembled into a single blob. This makes it possible to upload a large file in parallel, using multiple threads, which can improve upload performance. Once all the blocks have been uploaded, the blob is committed, and it becomes visible to users.
- Page Blobs: Page blobs are designed for random read/write operations and are typically used with virtual hard disks (VHDs) used by Azure virtual machines. Page blobs can store up to 8 TB of data, making them ideal for storing large VHDs. Page blobs are optimised for frequent read/write operations, making them well-suited for workloads that require low-latency access to data.
Unlike block blobs, page blobs are composed of 512-byte pages, which can be randomly read or written by a virtual machine. This makes them ideal for storing data that needs to be updated frequently, such as log files or database files.
- Append Blobs: Append blobs are designed for scenarios where new data needs to be added to an existing blob. For example, if you want to store log data, you can append new log entries to the end of an existing append blob. Append blobs can store up to around 195 GB of data.
Unlike block and page blobs, append blobs can only be written to sequentially. This means that once data has been appended to an append blob, it cannot be modified or deleted. This makes append blobs ideal for storing data that needs to be stored in a sequential manner, such as log files or sensor data.
In summary, block blobs are optimised for storing large files, page blobs are optimised for frequent read/write operations and are typically used with virtual machines, while append blobs are optimised for scenarios where new data needs to be added to an existing blob. Understanding the differences between these blob types can help you choose the right type of blob for your specific use case.