Restoring the MBR When Restoring a Backup

This question has no practical purpose. I'm only asking for my own understanding.

I'll use an illustration. Say I have a disk with two partitions - a system partition and a data partition. Now I decide to buy a new physical disk, so I can have my system on one disk and my data on the other disk. My plan is to restore an image of one of my partitions to the new disk.

Here's the part I don't understand. If, while restoring the image, I restore the original (backed up) MBR I have a problem because the partition table in that MBR has two partitions and the new disk only has one. If I restore a generic Windows MBR I also have a problem because the partition table in that MBR is blank, so how will it find my restored partition?

Obviously, there's something I'm missing. What is it?  Thanks for your help.



Hi Bulldog That's a great

Hi Bulldog

That's a great question!

The thing to keep in mind here is that when we talk about restoring the MBR, from the backup or using the generic WIndows one, we are only talking about the boot code in the MBR - not the Partition Table information. When we restore each partition to the disk, that is when we update the Partition Table in the MBR - essentially updating the offset of the start of the disk and marking the Active partition.

If you are thinking about adding an extra disk, it would be better to backup your Data volume and restore that to the new disk. If you have a large enough disk you can increase the size of the Data volume at the time of restore. Once you confirm it is OK you can delete the original Data volume and re-use the space (e.g. for the OS boot volume).

If you want to restore the Boot Volume (with OS on it) you are better off taking that drive out of the PC, attaching to the PC as a USB HDD, installing your new drive and performing a restore that way. If you know all is well on the restored OS, you can then delete the OS Boot Volume on original drive and plug the drive back into the machine. 

The one thing you want to avoid is keeping the oirginal HDD in the machine and performing a backup/restore of the Boot Volume to a second HDD. This will cause drive-letter conflicts in the registry of the restored volume that will then need to be fixed (e.g. by running HIR or Boot Configuration Utility, BCU)..





Aha. So when the


So when the ShadowProtect Restore Wizard asks about restoring the original MBR (from the backup image) or restoring the generic WIndows MBR, it actually refers to the boot loader of the MBR only - not the partition table information. After ShadowProtect restores the partition to the disk, it updates the partition table with information about that partition (which includes marking the partition as active, if that's the case.) 

Your other advice is sound and appreciated. It's definitely not a good idea to have two active partitions in a computer. It's like dating twins.

Thanks very much for your help.

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