Don’t forget to update your servers with update 1 and keep in mind that if you choose to update your clusters by hand. That you patch all the servers and not leave the cluster is a split-patched environment!. You will not be the first that have cluster troubles by mispatching.
now that there is a Update 1 you can see different patch models from 800 Mb to 3 MB depends on the update status from the machine.
Windows Server 2012 R2 Update is a cumulative set of security updates, critical updates and updates. You must install Windows Server 2012 R2 Update to ensure that your computer can continue to receive future Windows Updates, including security updates. For a complete listing of the issues that are included in this update, see the associated Microsoft Knowledge Base article for more information. After you install this item, you may have to restart your computer.
But if you don’t know the status of your servers and you don’t use wsus but patching from Microsoft update and there is no SCCM in place. you need some other tool to audit your servers. Write a Powershell script DSC or use a tool from codeplex Enter the PowerShell Patch Audit/Installation GUI (PoshPAIG).
This is a little toolkit that can do this for you If you don’t have tools in place and you need fast results this is the best way.
The tool is self explaining So I don’t go in to detail the source is here: http://poshpaig.codeplex.com/