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If I setup a VirtualBox guest with two 30 GB virtual hard disks and follow the following steps, the result will be a fully functional, booting operating system:

  1. Boot Ubuntu 14.04 Server install CD

  2. At the partioner, select 'manual'.

  3. Put a single empty partition on each virtual hard disk.

  4. Select 'Configure software RAID' from 'manual' menu.

  5. Add the two virtual hard disks, each with empty partitions, to a new RAID 1 pair and select 'finish.'

  6. Select 'Guided Partitioning' from 'manual' menu.

  7. Return to guided partitioning and select 'Guided - use entire disk and setup encrypted LVM.'

  8. Install to recently created software RAID device and use entire storage available for LVM.

  9. Finish installation.

However, take the steps above, but substitute Virtualbox guest for bare metal and substitute two virtual hard disks for two zeroed 3TB SATA disks, and the result is an un-bootable system. No GRUB screen, BIOS skips the disks.

I tried every possible combination of GPT flags, still nothing.

Any thoughts on the cause?

-Update-

So, the bare metal in question is a Lenovo x3100 M5 server with IBM firmware.

One hint to the problem, the Ubuntu server installer is dropping a BIOS compatible boot loader on the Virtualbox install.

On the Lenovo, it installs a uEFI GRUB, which, the Lenovo can boot as long as it is not on a mdadm RAID. If I follow the above steps on the Lenovo, minus the Ubuntu software RAID, it boots. If I configure the RAID 1 pair in the IBM firmware (c100/LSI fakeRAID), the install fails at the GRUB install.

Does not seem to be a GPT vs MBR issue since the Lenovo does boot the 3TB GPT LVM volume, as long as it is not on a RAID pair.

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  • Any reason why you're running RAID1 inside the VM? It gives really bad I/O performance as all writes are doubled and reads are distributed over the virtual disks, which may be on the same physical disk on the host. Is this just a test installation to see if you can do a RAID setup?
    – Simon Richter
    Nov 24, 2020 at 17:47
  • @SimonRichter yes it's a test. Look at the paragraph a little further on, "However, take the steps above, but substitute Virtualbox guest for bare metal and substitute two virtual hard disks for two zeroed 3TB SATA disks, and the result is an un-bootable system."
    – roaima
    Nov 24, 2020 at 18:03
  • @Simon - Thanks for waking up a zombie question–but to address your comment–the VM was simply to troubleshoot the issue. From what I remember, the dilemma comes down to the fact that you need a GPT partition table to boot a 2TB+ drive and uEFI won't boot a non MBR RAID pair. So if you want software RAID, you're stuck with 2TB or less.
    – medbot
    Nov 26, 2020 at 4:26

1 Answer 1

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Your 3TB disks need GPT boot rather than MBR, so you will need to allocate a 1MB BIOS boot partition for grub to store its data.

See http://ubuntuforums.org/showthread.php?t=2248346 for the gory details (which I will try to summarise here when I get back to a decent keyboard).

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  • I'd use 512MB as EFI partition, that way I'm not limited to grub -- other bootloaders such as systemd-boot copy the entire kernel and initrd to the ESP.
    – Simon Richter
    Nov 24, 2020 at 17:49

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