When booting Windows, the Windows Boot Manager menu will appear where you can select what disk to boot from. If you do not select a disk manually, the system will try to boot from the first one in 30 seconds:

• Windows Server 2016
• Windows Server 2016 – secondary plex

However, the problem is that the bootloader configuration is stored only on the first drive, and if you lose it you won’t be able to boot Windows from the second drive without additional actions. In fact, you have protected your data (but not the Windows bootloader) from a failure of the second disk only.

A software Windows RAID cannot be used to create a fully functional EFI partition mirror. Since the OS boot files are located on the EFI partition, if the first disk fails, you won’t be able to boot from the second disk without the manual repairing of your EFI bootloader. It is quite hard for a beginner and takes some time (you may not have it if there is a crowd of angry users around).

Now we’ll show you how to copy the EFI partition to the second disk and change the BCD bootloader configuration to enable booting Windows from both the first and second drives.

How to Create GPT Mirror for EFI Partition?

Then you have to prepare the EFI partition on the second disk in the mirror in order your computer can use this partition to boot Windows. Assign the drive letter S: to the EFI partition on Disk 1 and format it in FAT32:

Select disk 1
Select part 2
assign letter=S
format fs=FAT32 quick

Then assign the letter P: to the EFI partition on Disk 0:

select disk 0
select partition 2
assign letter=P
exit

How to Copy EFI partition and BCD Store to a Second Drive?

Display the current BCD bootloader configuration using the following command:

bcdedit /enum

When creating a mirror, VDS service has automatically added the BCD entry for the second mirror disk (labeled “Windows Server 2016 – secondary plex”).

In order to allow booting from EFI partition on the second disk if first disk failure, you must change your BCD configuration.

To do it, copy the current Windows Boot Manager configuration:

bcdedit /copy {bootmgr} /d "Windows Boot Manager Cloned"

The entry was successfully copied to {44d1d6bf-xxxxxxxxxxxxxxxx}

Then copy the configuration ID and use it in the following command:

bcdedit /set {44d1d6bf-xxxxxxxxxxxxxxxx} device partition=s:

If you have done it correctly, this message will appear:

The operation completed successfully.

List the current Windows Boot Manager (bcdedit /enum) configuration. Note that the bootloader is now having two options for boot from EFI partitions on different disks (default and resume object).

Then you must copy your BCD store from the EFI partition on Disk 0 to Disk 1:

P:
bcdedit /export P:\EFI\Microsoft\Boot\BCD2
robocopy p:\ s:\ /e /r:0

Rename the BCD store on Disk 1:

Rename s:\EFI\Microsoft\Boot\BCD2 BCD

And delete the copy on Disk 0:

Del P:\EFI\Microsoft\Boot\BCD2

If your first disk fails, you need to select the “Windows Boot Manager Cloned” item in the Windows Boot Manager (boot menu) and then “Microsoft Windows Server 2016 —? secondary plex” in order to boot your Windows correctly.

If one of the disks fails, you will get the Failed Redundancy message in Disk Management snap in.

In this case, you will have to replace the failed disk, delete the mirror configuration and create a software RAID 1 from the beginning.