title: Difficulty restoring a differential backup in SQL Server, 2 media families are expected or no files are ready for rollforward
body: <p>I have sql backups copied from server A to server B on a nightly basis.</p>
  
  <p>We want to move the sql server from server A to server B without much downtime, but the files are very large.</p>
  
  <p>I assumed that performing a differential backup and restore would solve the problem with the databases.</p>
  
  <ol>
  <li>Copy full backup from server A to copy to server B (10+gb)</li>
  <li>Open SQL Server Managment Studio on server B</li>
  <li>Right mouse on databases </li>
  <li>Restore Database </li>
  <li>Type in the new DB-name</li>
  <li>Choose "From Device" and browse to the backup file </li>
  <li>Click Okay. This is now resorting the original "full" backup.</li>
  <li>Test new db with dev application - everything works :)</li>
  <li>On original database rightmouse on DB > Tasks > Backup...</li>
  <li>Backup Type = Differential, Backup to disk, add a new file, and remove the old one (it needs to be a small file to transfer for the smallest amount of outage)</li>
  <li>Copy the diff backup onto the new db</li>
  <li>Right mouse on DB > Tasks > Restore > Database</li>
  </ol>
  
  <p>This is where I get stuck. If I add both the new differential file, and the original backup to the restore process I get an error</p>
  
  <pre><code>The media loaded on "M:\path\to\backup\full.bak" is formatted to support 1 media families, but 2 media families are expected according to the backup device specification.
  RESTORE HEADERONLY is terminating abnormally.
  </code></pre>
  
  <p>But if I try to restore using just the differential file I get</p>
  
  <pre><code>System.Data.SqlClient.SqlError: The log or differential backup cannot be restored because no files are ready to rollforward. (Microsoft.SqlServer.Smo)
  </code></pre>
  
  <p>Any idea how to do it? Is there a better way of restoring backups with limited downtime?</p>