Hey @MarkRelf-DB
Unfortunately it does not seem possible to move S3 Storage class to Azure Storage class.
Leveraging Auxiliary copy will be lengthy, however the biggest benefit will be ensuring data integrity during the move.
To limit data travelling over the network and reduce egress costs, I would recommend setting up a Cloud MA on the AWS side to perform reads from AWS Storage, and host a DDB for the Azure Storage. This way DDB Signature look ups can occur locally. You’d also want to migrate (if not already) the DDB assocaited with the AWS library and ensure the disk hosting these DDBs is capable of the required IOPs.
This will help ensure as little data as neccessary is being moved across the network, again, keeping costs down but also helping improve throughput and migration times.
This MA would be temporary and removed on completion of the migration after the Azure DDB is migrated back to your on-prem MA (the AWS DDB can be deleted along with the storage once all data is migrated accordingly).
Cheers
Jase