Windows dynamic disks and debian installer ?

September 22nd, 2011 by lucas

Windows has a feature called Dynamic Disks, which makes it ignore the DOS partition table and manage partitions its own ways. gparted is supposed to detect that, and warn the user that it can’t deal with that. The solution is to reboot in Windows, switch the partition back to “Basic disks”, and then proceed with installing Debian (or Ubuntu).

However, a student of mine had an interesting experience because gparted did not detect the dynamic disk stuff and did not warn about it, so the student went ahead with installing Debian squeeze. After reboot in Windows, Windows sees the partition as “invalid”. The same happens with Ubuntu 11.04 (not really surprising).

I’m surprised I did not find much information about that issue. Does someone has more info ?

The student was using two disks in his laptop, and only the second one (not the one used to boot windows) was using “dynamic disks”.

4 Responses to “Windows dynamic disks and debian installer ?”

  1. Elessar wrote on 09/22/11 at 11:44 am :

    I think Dynamic Disks is Microsoft’s implementation of a logical volume manager: http://en.wikipedia.org/wiki/Dynamic_disk .

    It should use DOS or GUID partitions, the same way Linux LVM does, using an internal block addressing system. The problem would be to resize them, as it would imply resizing the file system, then the logical partition, then the physical volume, and finally the underlying partition. As this is a Microsoft format, this should be done under Windows, which makes it problematic since it may not be possible to resize a mounted filesystem. And, as it is Microsoft, many features may be missing.

  2. Lucas wrote on 09/22/11 at 11:56 am :

    Ah, thanks for the wikipedia pointer, I failed to find it.

    I think that the student had left some free space on the disk, and did not try to resize the partition from the installer. However, after creating several partitions in the free space, it seems that writing the new MBR broke the dynamic disks partitions (maybe due to the non-standard geometry).

  3. Colin Watson wrote on 09/24/11 at 9:51 am :

    I think we’d need libparted to support this before d-i has a chance.

  4. pixelpapst wrote on 09/25/11 at 4:46 pm :

    Wikipedia notes:

    On a disk partitioned with the MBR Partition Table scheme, the Logical Disk Manager metadata are not stored in a partition, but are stored in a 1MiB area at the end of the disk that is not assigned to any partition.[3] The disc partitioning tools in Windows XP will not use that area for disk partitions, but the tools in other operating systems might.

    So I think your student probably created linux partitions all the way to the end, and overwrote his metadata area. Maybe we should just teach libparted to leave this area blank as a precaution.