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Block Blob vs Page blob vs Append Blob

Azure storage has three types of blobs namely Block blob (introduced in PDC2008 ), Page blob (introduced in PDC 2009) and Append blob (publically available in Q3 2015). The below table provides a comparison between them.

Block Blob

Page Blob

Append Blob

Block Blobs are comprised of blocks and each Block is identifiable by a Block IDPage blobs are collection of pages that are optimized for random read write operations.Append blobs are similar to block blobs but are optimized for Append operations
Usually used for streaming Sequential Data like VideoUsually used for non-Sequential Read and Write.Usually used for activities like Logging
Each Block can be up to 4 MBPage can be up to 512 bytesEach Block can be up to 4 MB
Up to 50,000 Blocks can be created.No limitations on the number of Pages createdUp to 50,000 Blocks can be created.
Blocks can be uploaded in any order and need to commit the blocks by sending the order at the end of the process. (A.K.A two-step block upload-then-commit process).Any writes that are done get committed immediately (in-place process)Cannot Update or delete the existing blocks in a blob.
Any uncommitted blocks will be deleted after a week time period or another blob with same name is created with commit process-NA--NA-
Any Uncommitted block can be over written by using the same block ID.Write operation can overwrite a page or a number of pages.Updating or overwriting a block is not possible.
Maximum Size of block blob : 195 GB

Maximum uncommitted blobs :100000 (Max size :20000MB)

Maximum size of page blob : 1TBMaximum size of page blob : 195 GB
Multiple clients writing to same blob is not possible (synchronization needed)Multiple clients writing to same blob is not possible (synchronization needed)Multiple clients writing to same blob is possible (no synchronization needed)
Most encountered Errors codes:

400 : Bad request – Invalid block or blob or block list

404 : Not Found – Container or blob not found

Most encountered Errors codes:

413 : Request Entity too Long – if the upload range is larger than 4 MB

416 : Request Range not satisifable

Most encountered Errors codes:

409-FeatureVersionMismatch – trying to access the append blob container with previous versions of service

References :

  1. Using Windows Azure Page Blobs and How to Efficiently Upload and Download Page Blobs
  2. MSDN – Introduction to Blobs
  3. Azure storage team blog
Published inAzure


  1. Abdul Abdul

    Great. Thanks for sharing the comparison.

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    • Vijayamanikandan Vijayamanikandan

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  3. Vijayamanikandan Vijayamanikandan

    Thanks. Great suggestions. I will certainly implement them.

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  5. vikranth vikranth

    what happen after reaching 195gb of page blob. will it automatically expand or we need to expand manually

  6. vikranth vikranth

    sorry append blob

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