Macrium Reflect: No operating system found after partition cloning

My objective is to have a windows 10 clone on a different disk in order to be able to continue working immediately in case of a disk failure.

1)Using Macrium Reflect in Windows 10 (1909), I cloned the windows partition (which is on a GPT disk) to partition J found on another disk (which was originally MBR and I converted it to GPT in Disk Management). I booted from the new disk and took "no operating system found, press ctrl+alt+del".

2)Using Macrium Reflect Rescue Media from a bootable usb stick, I restored an mrimg containing the windows partition to J (deleting the clone created in the previous step). Again, I took "no operating system found, press ctrl+alt+del".

3)I booted from the original disk and the new disk in Disk Management was saying "The disk is offline because it has a signature collision with another disk that is online" (I fixed it with right click > online).

Why 1 and 2 didn't work?
Thanks

i forgot to mention: When 1 and 2 happened, I had disconnected the original disk.

You need an EFI system partition on the target disk containing boot files (BCD) that points to the partition containing the OS on that disk.

Ok. How can I do that (with Macrium Reflect)?

Ghot said:

Make a full OS image backup of your Windows install (letting Macrium choose what partitions to include), and save it somewhere.

I have already done that, but instead of letting Macrium choose what partitions to include, I selected the C partition.

Ghot said:

Make a full OS image backup. Then go about your daily business. IF something happens to your Win 10 installation, then just put a spare drive in, and restore from the backup.

Ok, but I need to confirm it'll work.

Ghot said:

I think the problem you're having is that you are trying to have TWO Win 10 installations... with the same product key, available in the same computer at the same time.

As I wrote, I had disconnected the original win10 disk.

Ghot said:

I think the problem you're having is that you are trying to have TWO Win 10 installations... with the same product key, available in the same computer at the same time.

The problem is that there is no EFI system partition on the target (cloned) drive to boot from.

NavyLCDR said:

The problem is that there is no EFI system partition on the target (cloned) drive to boot from.

Thanks. How do I fix that?

George300 said:

Thanks. How do I fix that?

Since you asked previously how to do it with Macrium Reflect, you also have to clone the 100 MB FAT32 partition along with the C: drive partition. Then you may need to boot into a Macrium Reflect Rescue Drive and under the restore menu run the utility to Fix Windows boot problems to update the EFI system partition with the partition information for the cloned Windows C: drive partition.

However, there is a more efficient way, but to set it up nicely you will either need to repartition your target drive or use a tool like MiniTool Partition Wizard Free to create empty space on the target drive in front of (to the left of) the existing clone of C: drive on there.

The efficient way to do it is to have the target drive with the 16 MB Microsoft System Reserved (MSR) partition, followed by a 100 MB FAT32 EFI System Partition (ESP). Then, after that you can just clone your C: drive partition to the remaining space. Use the BCDBOOT command to set up booting from the ESP on the target drive. When you want to update your clone, you simply delete the C: drive cloned partition on the target drive, leave the MSR and ESP partitions alone. Re-clone your C: drive partition, and then re-run the BCDBOOT command.