Ubuntu
mdadm package

GPT Disk Conversion for mdadm/dual-boot system

Asked by Gus Zernial

I have a Kubuntu 12.04 system with three disks. The Kubuntu boot disk is /dev/sda and has one ext4 partition. On the other two disks /dev/sdb and /dev/sdc, the first partition is a Linux RAID partition, and I use Linux software Raid and mdadm to mirror these partitions in a RAID1 mirrored volume. The second partitions on /dev/sdb and /dev/sdc were ntfs partitions, on which I installed the Win7 boot disk C: and a Win7 data disk D: respectively. Thereafter I tried to upgrade to Win8, and, perhaps unfortunately, deleted the Win7 install on /dev/sdb (I haven't touched the Linux RAID partitions on the first partitions of /dev/sdb and /dev/sdc, and the Linux software RAID1 volume continues to work fine.

My system has a UEFI BIOS, and I found out in the process that to install Win8 on a UEFI system you have to create a UEFI-compatible Win8 USB flash install stick. OK, so I did that, and booted the Win8 install from that. The Win8 install started up, but when I select the NTFS partition on /dev/sdb, previously the Win7 C disk, and started the Win8 install, I get the error message "On EFI Systems, Windows can only be installed on GPT disks".

I take it that /dev/sdb and /dev/sdc are MBR disks, and I believe Linux supprts GPT disks and that there's a way to convert them to GPT disks with my NTFS partitions as before .... but I's unclear what this means for the Linux software RAID partitions. I believe GPT has a different scheme for disk boot sectors, and while I'm far from an expert on Linux software RAID, I have the impression that GPT changes the boot sector layout and that mdadm may have information on the boot sector, thus screwing up my RAID1 volume if I convert. Can anyone tell me if this can be done, and if so describe and/or point me to a link as to how? Thx, Gus

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actionparsnip (andrew-woodhead666) said : 		#1

Wow that Windows installer goes from strength to strength. I have no idea about the conversion but you can always run a final backup and wipe the drives, install Windows to a portion of the space and then install Ubuntu to the rest

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Gus Zernial (gus-zernial) said : 		#2

Don't get me started on Windows ..... I only use it because my work requires it .... anyway, one more question:

The /dev/sdb on which I want to install Win8 has one RAID partition, which is part of a Linux mdadm software RAID1 mirror, and a second partition for Win disk C:. So what about this ..... I reformat /dev/sdb with GPT and same size partitions. I use mdadm to restore the "destroyed" RAID1 mirror on /dev/sdb, by syncing it with the RAID partition on the other /dev/sdc disk. I then install Win8 on the second partition on /dev/sdb, which is now a GPT disk.

Would that work?

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