Reporting Services in SharePoint Integrated Mode with SSPI/Windows Authentication Architecture
Reporting Services in SharePoint Integrated Mode  can only be installed on a SharePoint Server. That is, you can only have the Reporting Services on the same server because Report Server database is no longer utilized when you install in SHP Integrated mode. Instead, SharePoint databases are used, there are a number of sharepoint databases used by SHP and one of them will host your meta data and report definitions. This makes centrally managing reports possible. So there is only one answer to your question, Server 2 or Sharepoint server.