The most current UEFI OS Deployment on a R810 is a bit finicky when you want to deploy Windows Server 2012 using the normal procedure & selecting “Other OS” as it’s obvious that the entry for Windows Server  2012 is not in there yet. The problem is that the Windows installer doesn’t seem to create the best practice UEFI partitions. It just seems to create a 320MB System Reserved partition and the rest is for your OS installation as Primary partition. In a good (by the book UEFI) install you’d see a layout like this (from Sample: Configure UEFI/GPT-Based Hard Drive Partitions by Using Windows Setup):

The reason for this seems to be that the firmware is still not 100% up to date for how Windows Server 2012 deals with UEFI installations. This I learned via my very helpful twitter friend Florian Klaffenbach

While an update for the system firmware is in the works and won’t be to long away let me share you how I dealt with this issue. It’s a bit more work but it get’s the job done. At least for me on a R810 with BIOS version 2.7.4.

I’m copying and adapting the step by step from Microsoft Windows Server 2012 Early Adopter Guide – Dell here and adapting it to how I worked around it. It’s “magic” .

Installing Using Dell Unified Server Configurator

1. Connect the keyboard, monitor, mouse, and any additional peripherals to your system
2. Turn on the system and the attached peripherals.
3. Press <F10> in the POST to start the System Services. The Initializing UEFI. Please wait… and the Entering System Services…Starting Unified Server Configurator messages are displayed.
4. In the Unified Server Configurator window, if you want to configure hardware, diagnostics, or set changes, click the appropriate option. If no changes are required, press OS Deployment. => you can opt to start with a cleanly build VDisk. Which is best and should suffice. But is doesn’t. We’ll clean the disk later anyway later on in Step 14.
5. In the Operating System Deployment window, click Deploy OS. The Configure or Skip RAID window is displayed. If Redundant Array of Independent Disks (RAID) is configured, the window displays the existing RAID configuration details.
6. Select Go directly to OS Deployment. If RAID is not yet configured, configure it at this time.
7. Click Next. The Select Operating System window is displayed with a list of compatible operating systems.
8. Choose Microsoft Windows Server 2012 and click Next.NOTE: If Microsoft Windows Server 2012 is not listed, choose any other operating system
9. Choose whether you want to deploy the operating system in UEFI or BIOS mode, and click Next => I do not get this choice if UEFI is already on in the BIOS settings
10. In the Insert OS Media window, insert the Windows Server 2012 media and click Next.
11. In the Reboot the System screen, follow the instructions on the screen and click Finish. If a Windows operating system is already installed on your system, the following message is displayed: Press any key to boot from the CD/DVD …Press any key to begin the installation. If you used a clean VDisk this is no issue
12. In the Windows Setup screen, select the appropriate option for Language, Time and Currency Format, and Keyboard or Input Method.
13. Click Next to continue.
14. STOP => Select to REPAIR your system and launch a command line. Form there you start diskpart and run following commands on the disk where you want to deploy Windows Server 2012:
    • select disk 0
    • clean
    • convert gpt

      In my case this is Disk 0. This is what the installer should be able to do automatically with a clean disk any way but it doesn’t happen.

      Now DO NOT navigate to the X: root and launch setup again. Shut exit the repair console and shutdown the server.

15. Start the server
16. Press <F10> in the POST to start the System Services. The Initializing UEFI. Please wait… and the Entering System Services…Starting Unified Server Configurator messages are displayed. => DO NOT TOUCH ANYTHING ANYMORE. It will take longer than expected but you will boot into the installation of Windows 2012 again.
17. In the Windows Setup screen, select the appropriate option for Language, Time and Currency Format, and Keyboard or Input Method.
18. Click Next to continue.
19. On the next page, click Install Now.
20. In the Operating System Install screen, select the operating system you want to install. Click Next. The License Terms window is displayed, click Next.
21. In the Which Type of Installation Do You Want screen, click Custom: Install Windows only (advanced), if it is not selected already.
22. In the Where do you want to install Windows screen, specify the partition on which you want to install the operating system. To create a partition and begin installation:
    1. Click New
    2. Specify the size of the partition in MB, and click Apply. A Windows might create additional partition for system files message is displayed. => NOW THE UEFI partitions on the GPT disk are created .
    3. Click OK.Select the newly-created operating system partition and click Next.
       The Installing Windows screen is displayed and the installation process begins. After the operating system is installed the system reboots. You must set the administrator password before you can log in for the first time
23. In the Settings screen, enter the password, confirm the password, and click Finish.
    The operating system installation is complete.

Now, while this worked for me on the Dell R810 with BIOS 2.7.4,  I give no guarantees whatsoever. You’ll have to test it yourself or wait for the firmware update that is coming soon. Any way, perhaps it helps some of you out there!