I can confirm that excatly the same happend to me with 6.10-server, i did not manage to figure out why it happend, but when i did set up MD under the installation of 5.10 it worked without any problems.
Alltough this was on the 32bit version running on a P4 2.6Ghz machine with 6x Samsung Spinpoint 200GB disks. ** Changed in: partman-md (Ubuntu) Status: Unconfirmed => Confirmed -- can't format software raid in edgy beta (amd64) https://launchpad.net/bugs/63235 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs