Uploading 'empty' blocks to page blobs is wasteful.

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 https://github.com/SUSE/azurectl/blob/master/azurectl/storage/page_blob.py#L50 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

[evanrolfe]

@bear454 FYI this feature has been implemented in commit https://github.com/Azure/azure-storage-python/commit/eb9183a20ba67cdbab868df3241258e93eb3cc3f

[zezha-msft]

This was fixed in release 1.0.0 of the blob package.