Changing file type from MBR to support GPT on BIOS configuration from Windows

Hello everyone,

I have a physical machine (Dell PowerEdge R420) server which I am connected to remotely (Server is in NYC). The server a has disk (5.5GB) but the GPT feature has not been enabled on it from the BIOS.

I tried converting the MBR to GPT using a software called EaseUS partition master but even after restarting the server it din't help.

Since the server is far away from me and I can't physically reach it.. I am wondering if there's any possible way to configure the BIOS from Windows to support GPT then convert the MBR To GPT on Windows.

Thanks a lot.
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Mohammed HamadaSenior IT ConsultantAsked:
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rindiConnect With a Mentor Commented:
Are you booting from the same disk? If that is the case you won't be able to convert the disk to GPT. In order to be able to boot to a GPT disk, windows needs the BIOS to be set to UEFI mode, and it also needs to be installed in that mode. That means if you need to boot Windows to a GPT disk you will have to do a fresh installation.

Most RAID controllers allow you to split a RAID array into more than one volumes. These Volumes appear to the OS as separate disks. That means you would then be able to boot into the first, smaller volume with it being setup as a standard MBR disk, while you can use the other Volume as a GPT disk for your data.

As the changing of your RAID configuration will probably blow away your data, you will still first have to make an image backup, then split the array into two volumes, and after that restore your system to the smaller volume from your backed up image. If you have configured your server's iDRAC module you should be able to do this remotely.
Manuel FloresCommented:
However, I believe that the main operating system disk can't be other thing that MBR... ?  let's check it out.
Manuel FloresCommented:
Some Windows operating systems cannot work with GPT hard disk, such as Windows 2000, XP, Windows 2003 32bit.

Is your case?
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Mohammed HamadaSenior IT ConsultantAuthor Commented:
I have windows 2012 R2. It does support GPT but windows is installed on MBR disk.
Manuel FloresConnect With a Mentor Commented:
PowerEdgeTechConnect With a Mentor IT ConsultantCommented:
Yes, you can change it to UEFI from within OMSA, but once you do, it will no longer boot to the installed OS. BIOS/Setup tab/Boot Settings. Once in UEFI mode, Server 2012 R2 should automatically convert the "disk" to GPT. You'll just have to be able to install via KVM or iDRAC since you will no longer have a working OS to connect to.
noxchoConnect With a Mentor Global Support CoordinatorCommented:
Take a screen shot of Windows Disk Management and post it here. You cannot simply convert the HDD with already installed Windows. As noted above it will not boot.
Thus only new installation. Or you connect another drive of smaller size to the server, clone the OS to it and then boot the server from new drive.
Then delete the OS and other partitions from 5.5TB drive and make it GPT.
Mohammed HamadaSenior IT ConsultantAuthor Commented:
Hi Noxcho, some software claim they can change the system disk from mbr to gpt like EaseUS partition master

however it seems that the BIOS I have on this machine is not in UEFI mode. as PowerEdgeTech indicated I think i'll lose the OS Since the BIOS change will change the file system type too.

I tried using EaseUS and GPTgen commandline but it didn't work.

I am posting a screenshot of the disk management and Ease US management UI. but since the BIOS is not set to UEFI then I am going to close the question and split points.

Thanks a lot everyone
Mohammed HamadaSenior IT ConsultantAuthor Commented:
The problem is a Windows GPT disk needs an EFI boot partition, plus needs to have been installed in EFI mode. That uses different files that don't get installed when you install the OS to an MBR disk. The install media also gets booted differently. So if you convert the disk from MBR to GPT the OS will no longer be bootable.

So your only option is to split your array into two volumes as I mentioned earlier, then restore the OS to the small MBR disk and use the larger volume as a GPT data disk, or install the OS again after you have created your GPT disk. As best practice is to have a small disk for the OS and a separate large disk for the data, splitting your array into 2 Volumes would be the best course of action anyway. Or as has also been mentioned, add two other small disks, create a RAID 1 array from those, and install or restore your OS to that new array.
noxchoGlobal Support CoordinatorCommented:
The software which you posted a link for, does convert the MBR drive into GPT however only DATA DRIVE. Not the system drive. That is the problem. That's why I was talking about second drive of smaller size for OS and then simply in Windows convert the bigger drive into GPT.
Remilekun OkegbenroCommented:
you can convert it from the installation menu of your OS in this case windows server 2012. but you need to ensure that you have a backup, because after converting it, you will have to format it. follow this steps:

1, boot from your installation disk
2, instead of install, choose repair
3,navigate to the command prompt.
4, on the command prompt type diskpart it will take you to a new environment
5, type list disk to view and select your disk drive
6, select the disk using the number of the disk as indicated
7, then type convert gpt

you can also use this steps to convert to mbr.
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