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Uploading 'empty' blocks to page blobs is wasteful.

See original GitHub issue

Re: PageBlobService#create_blob_from_stream

When a page blob is provisioned, the content is a stream of 0s. Therefore, when uploading a page blob, any block that is all zeros does not need to be uploaded, it can simply be skipped.

Most fixed-length VHD images are mostly empty blocks, so uploading all those zeros represents a huge waste of time and bandwidth.

Our optimum solution for dealing with this in azurectl was to load a block from /dev/zero and compare it to the current block in the stream. If they are equal… move along to the next block without uploading.

See for example.

And, just for reference, a 30GB openSUSE Leap 42.3 image, contains < 300MB of full blocks. Uploading with the API convenience methods, or az, results in an upload of 29.7GB of zeros. o.0

Issue Analytics

  • State:closed
  • Created 6 years ago
  • Reactions:1
  • Comments:7 (5 by maintainers)

github_iconTop GitHub Comments

evanrolfecommented, Jan 11, 2018
zezha-msftcommented, Jan 23, 2018

This was fixed in release 1.0.0 of the blob package.

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