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Windows 7: Convert GPT back to Basic Safely after attempt to create mirror?

12 Feb 2013   #1

Convert GPT back to Basic Safely after attempt to create mirror?

Hi All: I have a win7 sp1 x64 install with a second drive managed by Windows backup (with daily full backups enabled).

I wanted to migrate my boot partition ("Disk 0") over to a new SSD drive ("Disk 1"), and started to by creating a mirror of the c: volume. I used disk management and it prompted me to convert Disk 0 to dynamic which I did, and the mirror was created.

I can boot off Disk 1 (listed as "secondary plex"), but I can't pull Disk 0 since only the C: partition was mirrored and not the "system reserved". I tried "fixing" Disk 1 by using a system recovery disk, but I still can't boot from it without Disk 0 in place.

I found some technet instructions on how to properly do this on x64...using diskpart to recreate the MBR and BOOT partitions on the target disk BEFORE converting both discs to GPT and then mirroring the relevant partitions.

I would like to revert Disk 0 back to Basic and try again, but it seems like to do this the "Windows" way I would need to wipe all the volumes and restore from my backup/recovery discs. I would like to leave this as a "last resort" just in case I run into any problems there any other way to safely restore Disk 0 to "basic" from "dynamic"?

I've seen some 3rd-party software that claims to do this but am not sure if it's safe or if I will FUBAR the entire disk.

As a related there any way to reach the original goal (creating a mirror and then removing Disk 0) if Disk 0 is already dynamic?

My System SpecsSystem Spec
12 Feb 2013   #2


Just to follow up...I wiped Disk 1 using diskpart -> clean, and then in disk mgmt I was able to create a new mirror starting with the "system reserved" partition and then the "C" partition. The "c" partition is now "resynching" from Disk 0 to Disk 1.

Will this work now that I have the "system reserved" volume mirrored to Disk 1 along with "C"?

What I'd like to do is power down, pull Disk 0, boot from Disk 1 and eventually remove the mirror, so I'm running on Disk 1 exclusively. Will this work or am I headed for a world of pain?
My System SpecsSystem Spec
12 Feb 2013   #3

Microsoft Community Contributor Award Recipient


I wanted to migrate my boot partition ("Disk 0") over to a new SSD drive

Solved How to Migrate OS to new Hard disk.
My System SpecsSystem Spec

12 Feb 2013   #4
Microsoft MVP


If you mirrored the Disk then I don't know if Win7 will be intact if you try to convert it to Basic it may fail, but the way to do this non-destructively is download and burn to Cd the last version of Partition Wizard that still offers this as a free feature: ISO - Windows Live

Then boot the DVD and follow these steps: How to convert dynamic disk to basic disk with Partition Wizard?

If it fails follow these same steps to get a perfect Clean Reinstall - Factory OEM Windows 7
My System SpecsSystem Spec
12 Feb 2013   #5

Solved: creating mirror from GPT disk turned out to not be as bad as I thought...hopefully this will help anyone else facing the same issue.

After my original boot disk was converted to "Dynamic" from "Basic", there was no easy way using Windows' tools (e.g. diskpart.exe) to revert to "basic". However, I didn't have to.

Using diskpart.exe, I removed all the partitions from the new disk ("disk 1"), using:
diskpart> select disk 1
diskpart> clean
Using the Disk Management console, I then mirrored the "system reserved" partition from Disk 0 to Disk 1, and then mirrored the "C:" partition from Disk 0 to Disk 1. I then allowed the mirror to fully re-synch.

I shut down the computer and rebooted using "Secondary plex" (Disk 1) to confirm I could boot from the new disk. (I could)

I then shut down the computer again and removed Disk 0 and confirmed I could boot from Disk 1 (I could).

I then removed the mirroring on the two partitions and rebooted one more time to confirm the settings.

Finally, I used msconfig to remove the original system location on Disk 0 from the boot record, and now I can boot from the new disk as if it was the original system.

Lastly, I reconnected the original Disk 0, which still had a "D:" partition on it I wanted to preserve. When I rebooted and opened Disk Management console, the original Disk 0 showed up as "foreign disk" and did not mount, but the three partitions ("reserved", "C", and "D") were still there. I was able to "reactivate volume" and remount the original disk, so I cold continue to use the "D" partition or do whatever else I needed to do with it.
My System SpecsSystem Spec
12 Feb 2013   #6
Microsoft MVP


Glad you go it sorted.

For anyone else who finds this I gave the method just above for how to non-destructively convert Dynamic to Basic disk.
My System SpecsSystem Spec

 Convert GPT back to Basic Safely after attempt to create mirror?

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