Upgrading Windows Server 2012 to 2012 R2

System Requirements:

  • Windows Server 2012
  • Windows Server 2012 R2

The Problem:

This article outlines a few tips to be mindful of when performing an in-place upgrade from Windows Server 2012 to Windows Server 2012 R2.

More Info

Without wishing to be verbose on this one, the simple answer is that it appears to be a bug / limitation / “feature” of the iSCSI Target component of Server 2012. It was not a client issue.

Operating System Features

The following core features will not be available after upgrading from 2012 to 2012 R2

  • Servermanagercmd.exe
  • Slmgr.vbs
  • System Image Backup
  • Windows Server Resource Manager


The network profiles for non-domain adapters will drop back to Public after the upgrade, altering the active firewall configuration.


After the upgrade install, the Windows Firewall will inherit most firewall configuration settings from the previous configuration, however the port configurations for the iSCSI Target services will be in a disabled state, preventing your iSCSI Initiators from connecting to the service.

The upgrade process will fully de-install your NIC’s, although in general most of the main configuration settings are retained and re-applied after the upgrade (IP, Net mask etc), the advanced adapter settings are not applied. In particular, and Jumbo Frame settings designed to support extended MTU’s on your SAN NIC’s will have been reset to the standard 1500 bytes. This will have a performance hit on SAN access and Hyper-V live migration performance. You should manually re-enable the Jumbo frame settings (9014 or 9000 bytes) but be aware that it will cause the NIC to drop and re-initialise when you hit apply.


A number of the SysInternals apps, for example BGInfo, that work fine under 2012 have small issues under 2012 R2. BGInfo has a recent update that makes it aware of 2012 R2 and IE 11 rather than reporting that the OS is Windows 6.2 running MSIE 9.0.11.

WSUS 3.0 SP3

Ensure that any legacy WSUS 3.0 servers are patched to SP2 with KB2828185 installed. After re-synchronising, changing the product configuration and synchronising a second time that you server can update from your existing WSUS infrastructure. Be prepared for any 2012 R2 Data Center servers to report in WSUS as Windows 2000 Data Centre however!

Removing the Windows.old uninstall cache without installing Desktop Experience

Unfortunately you can no longer copy/paste the two cleanmgr.exe files out of WinSxS like you used to be able to do with 2008 (the store is compressed). I found that a few loops of the following will eventually remove the Windows.old upgrade cache from the root of the OS drive.

  :: This is very slow as it is disk intensive: run out of hours!!
  takeown /F C:\windows.old /R /D Y
  takeown /F c:\Windows.old\* /R /A /D Y
  takeown /F C:\windows.old /R /D Y
  takeown /F c:\Windows.old\* /R /A /D Y
  cacls C:\windows.old /T /G Administrators:F
  rd /s /q C:\windows.old

p.s. run each line manually, the above is not setup as a batch script and will ask for yes / no input. Several runs may be required.


Your desktop wallpaper will be reset to the default grey Windows Server logo, re-create as necessary

Don’t forget to activate against your KMS or enter your key.

Dell iDRAC 7 is now completely inaccessible to any of the 2012 R2 servers because IE11 is not yet supported. To run it, disable Protected mode and add the IP address of the DRAC server to the Compatibility Mode view