{"id":1435,"date":"2009-05-08T00:35:17","date_gmt":"2009-05-08T00:35:17","guid":{"rendered":"http:\/\/www.markwilson.co.uk\/blog\/2009\/05\/more-on-scdpm-and-agent-placement-in-a-virtualised-environment.htm"},"modified":"2009-05-08T00:35:17","modified_gmt":"2009-05-08T00:35:17","slug":"more-on-scdpm-and-agent-placement-in-a-virtualised-environment","status":"publish","type":"post","link":"https:\/\/www.markwilson.co.uk\/blog\/2009\/05\/more-on-scdpm-and-agent-placement-in-a-virtualised-environment.htm","title":{"rendered":"More on SCDPM and agent placement in a virtualised environment"},"content":{"rendered":"

Earlier this week, I wrote an introduction to System Center Data Protection Manager<\/a> (SCDPM). In that post, I mentioned that SCDPM 2007 SP1 supports Virtual Server 2005 R2 and Hyper-V virtualisation platforms but I’d like to elaborate on that and highlight the need to consider where best to deploy the SCDPM agents. <\/p>\n

With SCDPM 2007 SP1, we can back up Windows and non-Windows guest operating systems on either Virtual Server 2005 R2, Windows Server 2008 with the Hyper-V role enabled, or Hyper-V Server 2008. Depending upon the guest operating system, it will either be a VSS capable or a non-VSS capable guest .<\/p>\n

Linux, Windows NT, Windows 2000, Oracle and line of business applications will generally be non-VSS capable and in this case SCDPM will:<\/p>\n

    \n
  1. Hibernate the virtual machine to secure the memory and CPU contents to a saved state.<\/li>\n
  2. Take a snapshot of the virtual machine using the volume shadow copy service (VSS) – this takes just a few seconds (as the backup is taken from the snapshot, not the offline virtual machine).<\/li>\n
  3. Resume the virtual machine.<\/li>\n
  4. Use block level checksums to send only the changes within the VHDs (since the last backup) to the SCDPM server.<\/li>\n<\/ol>\n

    On a VSS capable guest operating system.<\/p>\n

      \n
    1. SCDPM contacts the VSS writer on the virtualisation host to request protection from the SCDPM agent, in the form of a referential VSS copy.<\/li>\n
    2. A query is performed via the integration components to instructs the VSS writer in the guest operating system (e.g. SQL Server VSS writer, Exchange Server VSS writer, Windows Server VSS writer) to create a consistent snapshot.<\/li>\n
    3. Only when the guest data is consistent and clean does the virtualisation layer provide SCDPM with a copy to backup from the host.<\/li>\n<\/ol>\n

      This referential VSS writer process means that:<\/p>\n