@Simion Brad Welcome to Microsoft Q&A Forum, Thank you postings your query here!
Yes, your procedure is correct and Azure File Sync should not download and overwrite all files on the new server. When you add the new Win 2k19 server endpoint to the existing Sync Group, Azure File Sync will compare the files on the new server with the files in the cloud and only download/upload the changes. Since the files on the new server are identical to the files in the cloud, Azure File Sync will not need to download/upload the entire 20TB of data.
However, it's important to note that the initial synchronization of the files on the new server may take some time, depending on the size of the changes and the speed of your network connection. During this time, users may experience some latency or performance issues when accessing the files on the new server.
Also, when you rename the new server with the old server name and IP address, you may need to update the DNS records and any other systems that reference the old server name and IP address to point to the new server. This will help to ensure that users are able to access the files on the new server without any issues.
Please let us know if you have any further queries. I’m happy to assist you further.
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