Subject: bug#21070: GPT backup corruption causes parted and linux installer to crash

From: Rod Smith <[email-masked]>
Date: Thu, 16 Jul 2015 13:36:02 -0400

On 07/16/2015 12:01 PM, [email-masked] wrote:

> I have bought 2x2TB disks and set it up for RAID0. I have installed
> Win7 first with UEFI that created GPT partitions.
...
> root@lubuntu:~# gdisk
> GPT fdisk (gdisk) version 0.8.8
> 
> Type device filename, or press <Enter> to exit: /dev/sda
...
> Command (? for help): p
> Disk /dev/sda: 3907029168 sectors, 1.8 TiB
> Logical sector size: 512 bytes
> Disk identifier (GUID): BFD8B9FE-8BF3-4AF3-B04C-326FC7FB5569
> Partition table holds up to 128 entries
> First usable sector is 34, last usable sector is 7812499934
> Partitions will be aligned on 2048-sector boundaries
> Total free space is 6890901949 sectors (3.2 TiB)

I've quoted some information that highlights issues that point to the
root cause of your problem:

* You've got 2x2TB in a RAID setup, so you should be seeing a
  disk device on the order of 4TB (~3.6TiB)
* gdisk says that the disk is 1.8TiB in size -- about the size
  of ONE of your two disks, NOT a RAID configuration.
* The partition table indicates that the last usable sector on
  the disk is 7,812,499,934, which works out to about 3.6TiB --
  so the original GPT was laid out with RAID active.

Overall, it looks like you're not using RAID from Linux. If this is
motherboard-based software RAID (aka "fake RAID"), you should NOT be
directly accessing /dev/sda, /dev/sdb, etc.; you should be using devices
in /dev/mapper, whose names vary depending on your chipset. Also,
sometimes Linux and Windows get out of sync on these drivers, so that
one OS activates the driver and the other doesn't. If you don't see
devices in /dev/mapper, you'll need to look into activating RAID in
Ubuntu. See the Ubuntu Community Wiki for advice on this topic:

https://help.ubuntu.com/community/Installation/SoftwareRAID

All that said, if a more up-to-date version of parted produces the
errors you report, that still constitutes a bug. As Brian Lane said,
though, your parted is a bit behind the times. This often happens when
you use a distribution-provided package, particularly for a long-term
support distribution like an Ubuntu LTS or a CentOS (vs. a non-LTS
Ubuntu or Fedora).

-- 
Rod Smith
[email-masked]
http://www.rodsbooks.com