Points of My Scenario:
1. I am both Windows admin and SQL Server sysadmin of two SQL Server 2016 servers.
2. Databases on Server-A are mirrored to Server-B: the servers are at different sites connected by WAN link .
3. Server-B needs to be replaced due to OS corruption that not even Microsoft can resolve.
4. The databases are too large to backup and send from Server-A to a new mirror partner server (e.g. Server-C).
5. I need the new server (Server-C) to use the mirrored database files on the problem Server-B to re-establish the mirror.
Note 1: Server-B is still running, but crashes regularly (2 - 3 times daily), and management wants it to be replaced before it stops running altogether.
Note 2: Server-C will need to be configured with the NetBIOS name of Server-B so that applications at the site will work if/when we fail-over.
QUESTION: How can I make a new server (Server-C) into a mirror partner for Server-A, using the database files from Server-B?
configure the mirror.
If your OS is corrup, I would not trust that as you never know whether the mirroring seized and they were out of sync. ...
Why use mirroring? look at whether Allways on is an alternative available to you. in a mirrored state server B's sql can only be used if it is an enterprise version and only if you take a snapshot of the existing mirror's state for purposes such as generating reports .....
backup\restrore to recovery is the only option available to you.
distance between the two location? If you are setting up server C. why not set it up on the same premises where Server A is using log shipping
preserving the transaction logs on server A and transferring /restoring them when server C is on site while leaving the DB in recovery mode, and then setting up the mirroring.
Another backup server A DB to an external storage/USB. transport it to where server C is restore from USB while in recovery and then see if there are transaction logs since to get the DB caught up before trying the mirror setup...