I am creating a disaster recovery plan for an Azure based application. In this application Azure Storage (BLOB, Gen purpose V2) has been used. We are using REST api to insert data inside the BLOB container. We are using GRS for redundancy. As per Azure documentation, the data is at first copied in the same region in 3 different availability zones synchronously. So my question is, when i upload a blob in azure storage using AZURE SDK or Rest api call and receive a success (200-OK) message, is it that the synchronous copy to all 3 availability zones in the same region is completed or only the copy to the first zone is completed and the remaining two are queued.
When you want your data to be replicated across AZs, you need to use ZRS (or GZRS for additional asynchronous replication to another region).
With ZRS, yes, your data is synchronously committed into three AZs and once you receive a 200-OK it means it has been written to all three zones. If you use GZRS, the additional replication to the secondary region then happens later.