Change HDD from MBR to GPT without losing data

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Change HDD from MBR to GPT without losing data

Postposted on Fri May 27, 2011 12:55 am

Hello, for some stupid reason, the OEM of my laptop used MBR on the HDD, leaving me with no ability to triple-boot (limited to 4 partitions, 3 are used to start with). I was wondering if it's possible to convert the partitions to GPT without losing any of the data. All of the guides I have seen say "back up all data, remove all of the MBR partitions, then convert it to GPT.", which I cannot do.

I have tried gptgen, however even though it says it's successful, it still leaves it as MBR.

Any help would be appreciated.
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Re: Change HDD from MBR to GPT without losing data

Postposted on Fri May 27, 2011 6:01 am

Shifting to a dynamic disk is an alternative to get around the four partition limit, but that may cause problems with non-Windows OS.

If a dynamic disk is unsuitable you'll have to empty the disk to convert to GPT. A GPT boot disk meanwhile introduces it's own set of strict limitations for Windows.

There's always virtuals machines instead of multi-boot configurations as well.
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Re: Change HDD from MBR to GPT without losing data

Postposted on Fri May 27, 2011 10:16 am

Unless dynamic disks work with Linux and OSX, I can't use them (I was planning on triple-booting OSX/Linux/Windows). I cannot use a VM because even with a 740qm the speed suffers a lot.
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Re: Change HDD from MBR to GPT without losing data

Postposted on Fri May 27, 2011 11:30 am

I've not used GPT myself; but according to Wikipedia, Windows and OSX only support booting from a GPT drive if you've got an EFI BIOS (or at least the GPT extensions part of it). Have you verified that your system has this?

Windows dynamic disks are likely a non-starter for Linux and OSX.

Why are three partitions already in use? That's the root of your problem.

What sort of things are you doing that make the performance of virtualized solutions unacceptable? Performance and stability of virtualization on modern CPUs is generally quite reasonable for the majority of tasks. Exceptions are anything that does tons of I/O, or 3D graphics (VM pass-through of GPU hardware acceleration is still a somewhat immature technology).
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Re: Change HDD from MBR to GPT without losing data

Postposted on Fri May 27, 2011 5:54 pm

What makes virtualized solutions unacceptable is that first, for Linux, I'm using it for programming. That means it should be able to compile and run in the quickest amount of time. Considering that the stuff I'm programming has to run in an emulator, the overhead of an emulator + vm would make it horribly slow. Also, I have tried OSX in VirtualBox, and it's much slower than on my 4-year-old mac that I have laying around.

I don't believe that I have an EFI BIOS, however I'm not sure. Also, 3 partitions were in use because 1 was for the bootloader, 1 was for the recovery partition, and one was for Windows. I don't want to wipe out the system recovery partition, or the bootloader partition, because that could cause issues with the system.
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Re: Change HDD from MBR to GPT without losing data

Postposted on Sat May 28, 2011 9:44 am

eliplan312 wrote:What makes virtualized solutions unacceptable is that first, for Linux, I'm using it for programming. That means it should be able to compile and run in the quickest amount of time. Considering that the stuff I'm programming has to run in an emulator, the overhead of an emulator + vm would make it horribly slow. Also, I have tried OSX in VirtualBox, and it's much slower than on my 4-year-old mac that I have laying around.

Do you have hardware virtualization enabled? The performance penalty really should not be that bad.

eliplan312 wrote:I don't believe that I have an EFI BIOS, however I'm not sure. Also, 3 partitions were in use because 1 was for the bootloader, 1 was for the recovery partition, and one was for Windows. I don't want to wipe out the system recovery partition, or the bootloader partition, because that could cause issues with the system.

The bootloader should not require its own partition, something is wrong there. If you have external restore media (DVD) you can get rid of the recovery partition; or image the whole drive if you don't have restore media and want the ability to get back to the current configuration.
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Re: Change HDD from MBR to GPT without losing data

Postposted on Sat May 28, 2011 12:39 pm

just brew it! wrote:The bootloader should not require its own partition, something is wrong there.


Windows 7 automatically creates a 100mb boot partition in order to support Bitlocker AKA whole disk encryption. Vista required the same thing, but did not created the boot partition by default as Windows 7 does.

So you're right from the perspective that he could get rid of it. I've never tried it, but it strikes me that 7's BCD repair option should probably be able to sort the situation out if the partition were to disappear.
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Re: Change HDD from MBR to GPT without losing data

Postposted on Sat May 28, 2011 1:48 pm

Ryu Connor wrote:
just brew it! wrote:The bootloader should not require its own partition, something is wrong there.

Windows 7 automatically creates a 100mb boot partition in order to support Bitlocker AKA whole disk encryption. Vista required the same thing, but did not created the boot partition by default as Windows 7 does.

So you're right from the perspective that he could get rid of it. I've never tried it, but it strikes me that 7's BCD repair option should probably be able to sort the situation out if the partition were to disappear.

Ahh, OK. Still seems he could get to where he needs to be by just removing the restore partition.

Another thought: I'm pretty sure it is possible to install Linux into an extended partition. If OSX will allow this as well, the whole issue is moot.
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Re: Change HDD from MBR to GPT without losing data

Postposted on Sat May 28, 2011 10:55 pm

I use GPT. However, I've never converted from one to another while keeping the data there. The quick fix is to image the recovery partition and then dump it. Long term reformatting GPT after you've moved your data.
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Re: Change HDD from MBR to GPT without losing data

Postposted on Mon May 30, 2011 7:06 pm

Yeah, I do have hardware virtualization enabled. Linux is still is noticeably slower (I need to be able to compile large tools (gcc, etc) quickly when they are updated, as I can't use the supplied binary packages for them).

Also, I needed to have the boot partition separate, because the Linux partition is at the end of the disk, and I don't want to screw around with the bootloader on the Windows partition. I guess I could remove the recovery partition, as I have backup drives.
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Re: Change HDD from MBR to GPT without losing data

Postposted on Mon May 30, 2011 7:17 pm

Yup... given your constraints, your best bet is to lose the recovery partition, provided you've got a way to get it back (or another way to reinstall the OS) if needed.
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Re: Change HDD from MBR to GPT without losing data

Postposted on Wed Jun 01, 2011 5:47 pm

Backed up the recovery partition to a 2tb external disk, and deleted it. Haven't seen any problems except having to repair the bcd/etc to get rid of the osx86 bootloader.
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