Hello Coffeng, René,
Thank you for posting your query here!
Adding on to the previous response, you can use AzCopy to copy your blobs across storage accounts. You can use SAS tokens to get access to storage accounts in different subscriptions.
Here's the how to guide:
https://zcusa.951200.xyz/en-us/azure/storage/common/storage-use-azcopy-blobs-copy?toc=/azure/storage/blobs/toc.json
You may consider Object replication; it asynchronously copies block blobs between a source storage account and a destination account.
Configure object replication for block blobs
Also, you can create an Azure Data Factory pipeline to copy data from the source storage account to the destination storage account.
Please let us know if you have any further queries. I’m happy to assist you further.
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