Blob storage (block, append, page) in Azure - Step-by-Step Execution

Process Flow - Blob storage (block, append, page)

Start: Choose Blob Type

↓

Append Blob Selected?

No→Page Blob Selected?

↓

Upload blocks

↓

Commit blocks

↓

Blob ready

↓

End

The flow starts by selecting the blob type. Depending on the type, data is uploaded differently: blocks for block blobs, appended for append blobs, and pages written for page blobs. Each ends with the blob ready for use.

Execution Sample

Azure

1. Select blob type: block
2. Upload block 1
3. Upload block 2
4. Commit blocks
5. Blob ready

This example shows uploading a block blob by uploading blocks and then committing them to finalize.

Process Table

Step	Action	Blob Type	Data State	Result
1	Select blob type	block	empty	Ready to upload blocks
2	Upload block 1	block	block 1 uploaded	Block stored temporarily
3	Upload block 2	block	block 1 and 2 uploaded	Blocks stored temporarily
4	Commit blocks	block	blocks committed	Blob finalized with blocks
5	Blob ready	block	committed blocks	Blob available for read/write
6	Select blob type	append	empty	Ready to append data
7	Append data chunk 1	append	chunk 1 appended	Data appended to blob
8	Append data chunk 2	append	chunks 1 and 2 appended	Data appended to blob
9	Blob ready	append	appended data	Blob available for append/read
10	Select blob type	page	empty	Ready to write pages
11	Write page 1	page	page 1 written	Page data updated
12	Write page 2	page	pages 1 and 2 written	Page data updated
13	Blob ready	page	written pages	Blob available for random read/write
14	Select blob type	invalid	empty	Error: Invalid blob type selected

💡 Execution stops after blob is ready or invalid blob type is selected.

Status Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	Final
blob_type	none	block	block	block	block
data_state	empty	block 1 uploaded	block 1 and 2 uploaded	blocks committed	committed blocks
blob_status	not ready	not ready	not ready	ready	ready

Key Moments - 3 Insights

Why do block blobs require committing blocks after uploading?

Because blocks are uploaded separately and only combined into a single blob after commit, as shown in steps 2-4 in the execution_table.

Can you append data to a block blob directly?

No, appending data is only supported by append blobs. Block blobs require uploading blocks and committing them, as seen in the execution_table steps for append vs block blobs.

Why must page blobs write data in pages?

Page blobs store data in fixed-size pages allowing random read/write access, so data must be written in page-sized chunks, as shown in steps 11-12.

Visual Quiz - 3 Questions

Look at the execution_table, what is the data_state after step 3?

A block 1 uploaded

B block 1 and 2 uploaded

C blocks committed

D empty

💡 Hint

Check the 'data_state' column for step 3 in the execution_table.

At which step does the blob become ready for append blob type?

A Step 9

B Step 7

C Step 8

D Step 6

💡 Hint

Look for 'Blob ready' with blob type 'append' in the execution_table.

If you select an invalid blob type, what happens according to the execution_table?

A Blob is ready immediately

B Data is uploaded anyway

C Error: Invalid blob type selected

D Blocks are committed automatically

💡 Hint

Check the last row of the execution_table for invalid blob type behavior.

Concept Snapshot

Blob storage types:
- Block blobs: upload blocks, then commit to finalize.
- Append blobs: append data chunks sequentially.
- Page blobs: write fixed-size pages for random access.
Choose type first, then upload data accordingly.
Each type suits different storage needs.

Full Transcript

Blob storage in Azure has three types: block, append, and page blobs. The process starts by selecting the blob type. For block blobs, you upload data in blocks and then commit these blocks to finalize the blob. Append blobs allow you to add data chunks sequentially without committing. Page blobs store data in fixed-size pages, enabling random read and write access. If an invalid blob type is selected, an error occurs and the process stops. This flow ensures data is stored efficiently based on the blob type chosen.